[IFCC-IUPAC/C-NPU documents | Contents]
The following text is based on the document published in Biochim Clin 1995; 19: 471-502.
The goals of the IUPAC Commission on Quantities and Units in Clinical
Chemistry (IUPAC-CQUCC)/IFCC Committee on Quantities and Units
(IFCC-CQU) (formerly Expert Panel on Quantities and Units - EPQU)
are to participate in the definition and of quantities and units
used for health care and related activities, and to ensure that
such quantities and units are consistent with standards promulgated
by authoritative international standards organizations in metrology.
To achieve these goals, a number of documents prepared by the
Commission/ Committee, with input from many clinical laboratory
scientists worldwide, have been published since 1967 (1 - 10).
A compendium of all these publications is currently in preparation.
Because of the importance of a consistent terminology in clinical
chemistry and because these documents are often published in journals
that may not be readily accessible, the Commission/Committee felt
that a glossary containing those terms considered of particular
use to the practising clinical chemist would be helpful to the
clinical chemistry and clinical laboratory science communities.
As a result, the glossary has been compiled from definitions taken
from published documents of the Commission/Committee (1-10).
Also it contains a number of terms, and their definitions, considered
relevant to the practice of clinical chemistry, taken from the
official documents of other commissions of IUPAC (11,
15, 17, 18)
and of international scientific organizations such as the International
Organization for Standardization (ISO) (12,
14), the International Bureau of Weights
and Measures (Bureau International des Poids et Mesures-BIPM)
(13, 14) and the International
Union of Biochemistry and Molecular Biology (IUBMB) ((16, (19).
For the sake of uniformity some definitions have been slightly modified from the original source. The entries are given in the form: Term, Symbol and Unit (for quantities).
The use of "round" parentheses () around words of some
terms means that these words may be omitted if it is unlikely
that this will cause confusion.
The use of "double square brackets"
is a result of describing Greek letters in HTML, f.ex.[[lambda]](Greek
letter "lambda" in italic (sloping)); [[Delta]]
(Greek capital letter "Delta" in upright (no sloping)).
An exception is the Greek letter µ.
Term | Symbol | Unit |
absolute activity | [[lambda]] | 1 |
Number defined by [[lambda]]_{B} = exp(µ_{B}/RT) when a component, B, is in a mixture of components (11), where:
µ_{B} = chemical potential of the component
R = molar gas constant
T = thermodynamic temperature
NOTES
Term | Symbol | Unit |
absorbance | A | 1 |
Negative logarithm of one minus absorptance as measured on a uniform sample (5).
NOTES
absorbance, lineic. See absorption coefficient.
Term | Symbol | Unit |
absorbed dose | D | Gy |
Energy imparted to matter by ionizing radiation in a suitable small element of volume divided by the mass of that element of volume (15).
Term | Symbol | Unit |
absorptance | [[alpha]] | 1 |
Radiant power absorbed by a system divided by the incident radiant power (5).
NOTES
absorption. See absorbance and absorption coefficient.
Term | Symbol | Unit |
absorption coefficient (linear) | a | m^{-1} |
Absorbance divided by the pathlength of a parallel beam within a uniform sample (5).
NOTES
Term | Symbol | Unit |
absorption coefficient (molar) | [[epsilon]] | m^{2} mol^{-1} |
Absorption coefficient (linear) due to a component divided by the amount-of-substance concentration of that component in moles (5).
NOTES
absorption factor. See absorptance.
Term | Symbol | Unit |
acceleration | a | m s^{-2} |
Rate of change of velocity (10).
NOTE. a = dv/dt
Term | Symbol | Unit |
acceleration of free fall | g | m s^{-2} |
Acceleration of free fall in vacuum due to gravity (10).
NOTE. Also called acceleration due to gravity.
activity. See (relative) activity.
Term | Symbol | Unit |
activity (of a radionuclide) | A | Bq |
Number of nuclear decays occurring in a given quantity of material in a small time interval, divided by the duration of that time interval (15).
Term | Symbol | Unit |
activity coefficient | [[gamma]] | 1 |
Number defined in terms of the (relative) activity a_{B} of the solute substance B in the solution by:
a_{M},B = [[gamma]]_{m},Bm_{B}/m- (T, p constant) (11)
when the solute substance (component), B, is in a solution containing molalities m_{B}, m_{C},..., of solute substances B, C, ..., in a solvent substance A, and m- is the standard molality.
NOTES
amount concentration. See substance concentration.
amount fraction. See substance fraction.
Term | Symbol | Unit |
amount-of-substance | n | mol |
Number of entities divided by the Avogadro constant (11).
NOTES
amount-of-substance concentration. See substance concentration.
amount-of-substance content. See substance content.
amount-of-substance fraction. See substance fraction.
Term | Symbol |
ampere | A |
Base unit of the SI for electric current, equal to that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross section, and placed 1 metre apart in vacuum, would produce between those conductors a force equal to 2 · 10^{-7} newton per metre of length (13).
Term | Symbol | Unit |
angle | [[alpha]], [[beta]], [[gamma]], J, .... | rad |
Ratio of the arc cut out in a circle with its centre at that point to the radius of the circle (12).
NOTES
Term | Symbol |
ångström | A |
Non SI unit of length equal to 10^{-10}m.
NOTE. The unit is recognized by the CIPM for temporary use with the SI until considered no longer necessary (13).
Term | Symbol | Unit |
area | A | m^{-2} |
A = || dx dy(12).
areic. Modifier used to denote divided by area (7).
Term | Symbol |
atmosphere, standard | atm |
Non SI unit for pressure, defined by: 1 atm = 101 325 Pa (13).
Term | Symbol | Unit |
atomic mass | m_{a} | kg |
Mass of an atom of a stated nuclide in its nuclear and atomic ground state (11).
NOTE. Also called the rest mass of an atom.
Term | Symbol | Unit |
atomic mass constant | m_{u} | kg |
Constant equal to 1/12 of the rest mass of a neutral atom of the nuclide ^{12}C in its nuclear and atomic glound state (11).
NOTE. The atomic mass constant is equal to one unified atomic mass unit (11).
atomic mass unit. See unified atomic mass unit.
Term | Symbol | Unit |
atomic number | Z | 1 |
Number of protons contained in an atomic nucleus (12).
NOTE. Also known as proton number.
atomic weight. See relative atomic mass.
Term | Symbol | Unit |
attenuance | D | 1 |
Negative logarithm of transmittance of a parallel beam through a uniform sample (5).
NOTES
Term | Symbol | Unit |
attenuation coefficient (linear) | m | m^{-1} |
Attenuance, D, divided by the pathlength, l, of a parallel beam through a sample of uniform properties (5).
NOTES
Term | Symbol |
atto | a |
Prefix used with SI units to denote 10^{-18} (13).
Term | Symbol | Unit |
Avogadro constant | L, N_{A} | mol^{-1} |
Number of entities in a system divided by the amount-of-substance of those entities (11).
NOTE. L = N/n = 6,022 136 7(36) · 10^{23} mol^{-1}
Term | Symbol |
bar | bar |
Non SI unit for pressure equal to 10^{5} Pa (13).
NOTE. Approved by the CIPM for temporary use with SI units until considered no longer necessary (13).
base quantity. One of the quantities that, in a system of quantities, are conventionally accepted as functionally independent of one another (14).
base unit (of measurement). Unit of measurement of a base quantity in a given system of quantities (14).
NOTE. See unit (of measurement).
Term | Symbol |
becquerel | Bq |
SI unit of (radio)activity, equal to one nuclear decay per second (13).
Term | Symbol | Unit |
Boltzmann constant | k | J K^{-1} |
Molar gas constant divided by the Avogadro constant (11).
NOTES
Term | Symbol |
calorie | cal |
Unit for energy (heat) whose use with the International System of Units is generally deprecated (13).
NOTES
Term | Symbol |
candela | cd |
Base unit of the SI for luminous intensity, equal to the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 · 10^{12} hertz and that has a radiant intensity in that direction of (1/683) watt per steradian (13).
Term | Symbol | Unit |
capacitance | C | F |
Electrical charge divided by potential difference (12).
Term | Symbol | Unit |
catalytic activity | z | kat |
Increase in the rate of reaction of a specified chemical reaction that an enzyme produces in a specific assay system (16).
NOTE. See rate of reaction.
Term | Symbol | Unit |
catalytic activity concentration | b | kat m^{-3} |
Catalytic activity of the component divided by the volume of the system (2).
NOTES
Term | Symbol | Unit |
catalytic activity content | z/m | kat/kg |
Catalytic activity of the component divided by the mass of the system (2).
NOTES
Term | Unit |
catalytic activity fraction | 1 |
Quotient of the catalytic activity of the isozyme and the catalytic activity of all the isozymes of the same enzyme in the system.
NOTES
catalytic concentration. See catalytic activity concentration.
catalytic content. See catalytic activity content.
catalytic fraction. See catalytic activity fraction.
Term | Symbol | Unit |
Celsius temperature | t | °C |
Difference in the thermodynamic temperature of a body and the thermodynamic temperature of the triple point of water, minus 0,01 K (12).
NOTES
Term | Symbol |
centi | c |
Prefix used with SI units to denote 10^{-2} (13).
Term | Symbol | Unit |
centripetal acceleration | a_{rot} | m s^{-2} |
Acceleration of a component as a result of a uniform rotational motion (10).
Term | Symbol | Unit |
centrifugal force | F_{rot} | N |
Fictisious force acting on a body as a result of centripetal acceleration (10).
Term | Symbol | Unit |
centrifugal radius | r | m |
Distance from the axis of rotation at which the component is spinning at the end of centrifugation (10).
charge. See electric charge and elementary charge.
Term | Symbol | Unit |
charge number (of an ion) | z | 1 |
Ratio of the electric charge carried by an ion to the elementary charge (18).
chemical amount. See amount-of-substance.
Term | Symbol | Unit |
chemical potential | µ | J mol^{-1} |
Quotient of the differential change in the internal energy of a component in a system and the differential change in the amount-of-substance of the component, maintaining other extensive quantities constant (4).
Term | Symbol | Unit |
clearance | [[Delta]]V/[[Delta]]t | m^{3} s^{-1} |
Product of the concentration of a component in the output system and the volume flow rate of that output system divided by the concentration of this component in the input system (2).
NOTES
coefficient. Proportionality constant, k, in a multiplicative relationship between two quantities, A and B, having different dimensions, (A = k · B) (12).
NOTE. When the quantities A and B have the same dimension the proportionality constant is called a factor.
coherent system of units (of measurement). System of units of measurement in which all of the derived units are coherent (14).
NOTE. See coherent unit (of measurement) and derived unit (of measurement).
coherent (derived) unit (of measurement). Derived unit of measurement that may be expressed as a product of powers of base units with the proportionality factor one (14).
Term | Symbol |
component | A, B,....N |
Stated part of a system (2).
NOTES
concentration. See substance concentration.
Term | Symbol | Unit |
concentration gradient | grad C | m^{-4} |
Differential change in concentration of a component in a given direction in a small distance divided by the distance in that direction (10).
NOTES
Term | Symbol | Unit |
conductance | G | S |
Reciprocal of the electrical resistance of a conductor (12). See resistance.
Term | Symbol | Unit |
conductivity | [[gamma]] | S m^{-1} |
Reciprocal of the resistivity of a conductor (12). See resistivity.
content. See substance content.
conventional true value (of a quantity). Value attributed to a particular quantity and accepted, sometimes by convention, as having an uncertainty appropriate for a given purpose (14).
Term | Symbol |
coulomb | C |
SI unit for electric charge, equal to the electric charge carried in one second by a constant current of one ampere (13).
Term | Symbol |
curie | Ci |
Non SI unit for the activity of a radionuclide, corresponding to 3,7 · 10^{10} disintegrations per second (13).
NOTES
current density. See electric current density.
cycles per second. See hertz.
Term | Symbol |
dalton | Da |
Non SI unit equal to one unified atomic mass unit (11).
NOTES
Term | Symbol |
day | d |
Non SI unit for time equal to 86 400 seconds (13).
NOTE. Because of its importance and wide use, the CIPM approved the use of the day with SI units (13).
Term | Symbol |
deca | da |
Prefix used with SI units to denote 10^{1} (13).
decay constant. See disintegration constant.
Term | Symbol |
deci | d |
Prefix used with SI units to denote 10^{-1} (13).
Term | Symbol |
degree | ° |
Non SI unit for plane angle, equal to [[pi]]/180 rad (13).
NOTE. Because of its importance and wide use, The CIPM approved use of the degree with SI units (13).
Term | Symbol |
degree Celsius | °C |
Special name used in place of kelvin to express Celsius temperature (13).
Term | Symbol | Unit |
degree of dissociation | [[alpha]] | 1 |
Ratio of the number of dissociated molecules of a substance to the total number of molecules (12).
Term | Symbol | Unit |
density | [[rho]] | kg m^{-3} |
Mass of a substance or body divided by its volume (11).
NOTES
derived quantity. Quantity defined, in a system of quantities, as a function of base quantities of that system (14).
NOTE. See quantity and base quantity.
derived unit (of measurement). Unit of measurement of a derived quantity in a given system of quantities (14).
NOTES
Term | Symbol | Unit |
diffusion coefficient | D | m^{2} s^{-1} |
Absolute value of the product of the local number concentration of a component and the local average velocity of particles of that component divided by the number concentration gradient in the direction of movement (10).
dimension (of a quantity). Expression that represents a quantity of a system of quantities as the product of powers of factors that represent the base quantities of the system (14).
NOTE. See base quantity.
dimensionless quantity. See quantity of dimension one.
Term | Symbol | Unit |
disintegration constant | [[lambda]] | s^{-1} |
Probability of disintegration in a small time interval divided by the duration of the time interval (12).
NOTES
Term | Symbol | Unit |
distribution constant | K_{D} | 1 |
Quotient of the concentration of a component in a single definite form in an organic solvent phase, or in the chromatographyc stationary phase, and its concentration in the same form in the aqueous phase, or in the chromatographic mobile phase, at equilibrium (17).
NOTES
Term | Symbol | Unit |
distribution ratio | D | 1 |
Quotient of the amounts of a component in two phases (17).
NOTES
dose. See absorbed dose and dose equivalent.
Term | Symbol | Unit |
dose equivalent (effective of radiation) | H | Sv |
Absorbed dose multiplied by a quality factor and the product of all other modifying factors, aimed at expressing on a common scale, for different types of radiations and distributions of absorbed dose, the biological effects associated with exposure (15).
NOTE. See also absorbed dose.
dynamic viscosity. See viscosity.
electric capacitance. See capacitance.
Term | Symbol | Unit |
electric charge | Q | C |
Integral of electric current over time (12).
NOTE. See electric current.
electric conductance. See conductance.
electric conductivity. See conductivity.
Term | Symbol | Unit |
electric current | I | A |
Base quantity of the International System of Units (12).
NOTE. See Systéme International d'Unités.
Term | Symbol | Unit |
electric current density | J | A m^{-2} |
Electric current divided by area (12).
NOTES
Term | Symbol | Unit |
electric field strength | E | V m^{-1} |
Force exerted by an electric field on a point charge divided by the electric charge (12).
electric mobility. See mobility.
Term | Symbol | Unit |
electric potential difference (of a galvanic cell) | [[Delta]]V | V |
Difference in the potentials of electrodes on the right and left of a galvanic cell (11).
NOTE. When [[Delta]]V is positive, positive charge flows from left to right through the cell.
electric resistance. See resistance.
electric resistivity. See resistivity.
Term | Symbol | Unit |
electrode potential | E | V |
Electromotive force of a cell in which the electrode on the left is a standard hydrogen electrode and the electrode on the right is the electrode in question (11).
Term | Symbol | Unit |
electrokinetic potential | [[zeta]] | V |
Electric potential difference between the fixed charges on the immobile support and the diffuse charge in the solution (9).
NOTE. Also called zeta potential.
Term | Symbol | Unit |
electromotive force | E | V |
Energy supplied by a source divided by the electric charge transported through the source (12).
Term | Symbol |
electronvolt | eV |
Kinetic energy acquired by an electron passing through a potential difference of one volt (13).
NOTES
electrophoretic mobility. See mobility.
Term | Symbol | Unit |
elementary charge | e | C |
Electric charge of a proton (12).
NOTES
Term | Symbol | Unit |
emittance | [[epsilon]] | 1 |
Radiant exitance of a sample divided by the radiant exitance of a black body at the same temperature (5).
NOTES
Term | Symbol | Unit |
enthalpy | H | J |
Thermodynamic quantity qiven by the sum of the internal energy and the product of the pressure and volume of a system (12).
entitic. Modifier used to denote divided by number of entities (7).
Term | Symbol | Unit |
entropy | S | J K^{-1} |
Quantity defined by dS = dQ/T when an amount of heat dQ is received by a system having a thermodynamic temperature T, provided that no irreversible change takes place in the system (12).
enzyme activity. See catalytic activity.
Term | Symbol | Unit |
equilibrium constant (concentration) | K_{c} | (mol m^{-3})^{[[Sigma]][[upsilon]]} |
Product of the substance concentrations of the components of a specified reaction to the power of their stoichiometric numbers in the reaction equation (11).
NOTES
Term | Symbol |
erg | erg |
Non SI unit for energy (13).
NOTES
Term | Symbol |
exa | E |
Prefix used with SI units to denote 10^{18} (13).
Term | Symbol | Unit |
extent of reaction | [[Delta]][[xi]] | mol |
Change in the amount-of-substance of a component divided by the stoichiometric coefficient of the component (11).
NOTES
extinction. Sum of the effects of absorption, scattering, and luminescence (11).
NOTE. Use of the term extinction to denote absorbance is deprecated by IUPAC.
extinction coefficient. See absorption coefficient (linear).
NOTE. Use of the term extintion coefficient to denote absorption coefficient is deprecated by IUPAC.
factor. Proportionality quantity, k, in a multiplicative relation between two quantities, A and B, having the same dimension, A=k · B (12)
NOTE. When the quantities A and B have different dimensions the proportionality quantity is called a coefficient.
Term | Symbol |
farad | F |
SI unit for capacitance, equal to the capacitance of a capacitor between the plates of which there appears a potential difference of 1 V when it is charged by a quantity of electricity of 1 C (13).
NOTE. 1 F = m^{-2} kg^{-1} s^{4} A^{2}.
Term | Symbol | Unit |
Faraday constant | F | C mol^{-1} |
Product of the Avogadro constant and the charge of the proton (11).
Term | Symbol |
femto | f |
Prefix used with SI units to denote 10^{-15} (13).
Term | Symbol | Unit (of X) |
flux | J_{X} | s^{-1} m^{-2} |
Rate of movement of a quantity X per area of surface normal to flow, or interface through which the movement is taking place (11).
NOTES
Term | Symbol | Unit |
force | F | N |
Vector quantity equal to the product of the mass of a body and its acceleration (10).
NOTE. F = m(dv/dt) = m a
Term | Unit |
fraction | 1 |
Quotient where the numerator quantity refers to a component while the denominator is a quantity of the same kind for the whole system (7).
NOTE. From the definition, a fraction has a value between zero (included) and one (included).
Term | Symbol | Unit |
frequency | J | Hz |
Number of regular events in a given time divided by that time (12).
NOTE. For electromagnetic radiation the frequency is related to photon energy by E = hJ, where is the Planck constant. Frequency is also related to the speed of light, c, and the wavelength, [[lambda]] by the expression J = c/[[lambda]] (11).
friction coefficient. See friction factor.
Term | Symbol | Unit |
friction factor | µ | 1 |
Quotient of frictional force and normal force, for a sliding body (12).
NOTE. Formerly called frictional coefficient or coefficient of friction.
gas constant. See molar gas constant.
Term | Symbol | Unit |
Gibbs energy | G | J |
Thermodynamic quantity equal to the difference between the enthalpy of a system and the product of the thermodynamic temperature to the entropy of this system (12).
Term | Symbol |
giga | G |
Prefix used with SI units to denote 10^{9} (13).
Term | Symbol |
gram | g |
Base unit for mass in the CGS system of units (13).
NOTES
Term | Symbol |
gray | Gy |
SI unit for absorbed dose of radiant energy, equal to one joule per kilogram (13).
NOTE. The gray is a special unit of the SI permitted by the GIPM for reasons of safeguarding human health (13).
Term | Symbol | Unit |
half life | T_{1/2} | s |
Average time required for the exponential decay of one half of the atoms of a sample of a radionuclide (12).
NOTES
Term | Symbol | Unit |
heat capacity | C | J K^{-1} |
Quantity equal to dQ/dT, where dT is the increase in thermodynamic temperature as a result of the addition of an amount of heat dQ to a system (12).
Term | Symbol |
hecto | h |
Prefix used with SI units to denote 10^{2} (13).
Term | Symbol |
henry | H |
Inductance of a closed circuit in which an electromotive force of 1 volt is produced when the electric current in the circuit varies uniformly at the rate of 1 ampere per second (13).
NOTES
Term | Symbol |
hertz | Hz |
SI unit for frequency, equal to one cycle per second (13).
Term | Symbol |
hour | h |
Non-SI unit for time, equal to 3 600 s (13).
NOTE. Because of its importance and wide use, the CIPM approved use of the hour with SI units (13).
Term | Symbol | Unit |
illuminance | E | lx |
Luminous flux incident on an element of a surface, divided by the area of that element (12).
Term | Symbol | Unit |
impedance | Z | [[Omega]] |
Complex representation of potential difference divided by the complex representation of current (12).
NOTE. See resistance.
Term | Symbol | Unit |
internal energy | U | J |
Quantity defined as the sum of the heat Q added to a system and the work W done on the system (11).
NOTE U = Q + W. When Q > 0 and W > 0 there is an increase in the internal energy of the system.
Term | Symbol |
international calorie | cal_{IT} |
Non-SI unit for energy, equal to 4,186 8 J (13).
NOTES
International System of Units. See Système International d'Unités.
Term | Symbol |
international unit | int. unit |
Arbitrary unit for a measurement that is agreed upon by the World Health Organization (2).
NOTE. Frequently used to express the results of measurement of a biological activity of a component.
ionic concentration. See ionic strength (concentrational).
Term | Symbol | Unit |
ionic strength (concentrational) | I_{c} | mol m^{-3} |
One half the product of the concentration of an ion and its charge to the power 2 (11).
NOTES
Term | Symbol | Unit |
ionic transport number | t | 1 |
Quotient of the current carried by an ionic component and the total current (12).
NOTE. For clinical chemistry the term component is recommended (2), ISO uses substance.
Term | Symbol | Unit |
irradiance | E | W m^{-2} |
Radiant power received by an element of surface divided by the area of that element (5).
NOTE. See radiant exitance.
Term | Symbol |
joule | J |
SI unit for energy, equal to the work done when the point of application of a force of one newton is displaced through a distance of one metre in the direction of the force (13).
NOTE. 1 J = 1 N m = 1 m^{2} kg s^{-2}.
Term | Symbol |
katal | kat |
Unit for catalytic activity coherent with the SI, equal to the catalytic activity that catalyzes a reaction rate of one mole per second in an assay system (16).
NOTES
Term | Symbol |
kelvin | K |
Base unit of the SI for thermodynamic temperature, equal to the fraction 1/273,16 of the thermodynamic temperature of the triple point of water (13).
Term | Symbol |
kilo | k |
Prefix used with SI units to denote 10^{3} (13).
Term | Symbol |
kilogram | kg |
Base unit of the SI for mass, equal to the mass of the international prototype of the kilogram (13).
NOTE. The names of the multiples and sub-multiples of the unit of mass are formed by adding the prefixes to the word gram.
kind-of-quantity. Abstract property common to several real quantities (2). See quantity.
Term | Symbol | Unit |
kinetic energy | E_{k} | J |
Energy of a body due to motion (11).
NOTE. E = 1/2mv^{2}
Term | Symbol | Unit |
kinematic viscosity | [[Theta]] | m^{2} s^{-1} |
Quotient of the viscosity and the density (11).
Term | Symbol | Unit |
length | l | m |
Base quantity of the international system of units (12).
NOTE. See Systeme International d'Unités.
life-time. See mean life.
linear absorption coefficient. See absorption coefficient (linear).
linear attenuation coefficient. See attenuation coefficient (linear).
lineic. Modifier used to denote divided by length (7).
lineic absorbance. See absorption coefficient (linear).
Term | Symbol |
litre | l or L |
Non SI unit for volume, equal to 10^{-3} m^{3} (13).
NOTES
Term | Symbol |
lumen | lm |
SI unit for luminous flux, equal to the luminous flux emitted in unit solid angle (steradian) by uniform point source having a luminous intensity of 1 candela (13).
NOTE. 1 lm = 1 cd sr
Term | Symbol | Unit |
luminous flux | d[[phi]] | lm |
Quantity defined as I · d[[Omega]], where I is the luminous intensity in an element of solid angle d[[Omega]], of a source (12).
Term | Symbol | Unit |
luminous intensity | I | cd |
Base quantity of the International System of Units (12).
NOTE. See Système International d'Unités.
Term | Symbol |
lux | lx |
SI unit for illuminance, equal to one lumen per square metre (13).
NOTE. 1 lx = 1 m^{-2} cd sr
Term | Symbol | Unit |
mass | m | kg |
Base quantity of the International System of Units (12).
NOTES
Term | Symbol | Unit |
mass concentration | [[rho]] | kg m^{-3} |
Mass of the component divided by the volume of the system (2).
NOTES
Term | Symbol | Unit |
mass density | [[rho]] | kg m^{-3} |
Mass of a system divided by its volume (10).
NOTE. The name volumic mass is recommended for this quantity (7).
Term | Symbol | Unit |
mass density gradient | grad [[rho]] | kg m^{-4} |
Change in mass density in a small distance divided by that distance (10).
Term | Symbol | Unit |
mass flow rate | q_{m} | kg s^{-1} |
Mass of a mater crossing a surface divided by the time (12).
Term | Symbol | Unit |
mass fraction | w | 1 |
Quotient of the mass of a component and the mass of the system containing the component (12).
NOTES
Term | Symbol | Unit |
mass number | A | 1 |
Number of nucleons in an atomic nucleus (12).
NOTE. Also called nucleon number.
massic. Modifier used to denote divided by mass (7).
Term | Symbol | Unit |
mean life | [[tau]] | s |
Number of entities of a component in a system at equilibrium divided by the number of entities of the component being transformed per time (18).
NOTES
mean volume rate. See clearance.
measurand. Particular quantity subject to measurement (14).
Term | Symbol |
mega | M |
Prefix used with SI units to denote 10^{6} (13).
Term | Symbol |
metre | m |
Base unit of the SI for length, equal to the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second (13).
Term | Symbol | Unit |
Michaelis constant | K_{m} | mol m^{-3} |
Substance concentration of substrate at which the rate of reaction is equal to one half of the limiting rate (maximum rate) (19).
NOTES
Term | Symbol |
micro | µ |
Prefix used with SI units to denote 10^{-6} (13).
Term | Symbol |
milli | m |
Prefix used with SI units to denote 10^{-3} (13).
Term | Symbol |
millimetre of mercury | mmHg |
Non SI unit for pressure (13).
NOTES
Term | Symbol |
minute (of arc) | ' |
Non SI unit for plane angle, equal to ([[pi]]/10 800) rad (13).
NOTE. Because of its importance and wide use, the CIPM approved use of the minute of arc with SI units (13).
Term | Symbol |
minute (of time) | min |
Non SI unit for time, equal to 60 s (13).
NOTE. Because of its importance and wide use, the CIPM approved use of the minute of time with SI units (13).
Term | Symbol | Unit |
mobility (electric) | µ | m^{2} V^{-1} s^{-1} |
Average drift velocity imparted to a charged particle in a medium by the electric field divided by the field strength (11).
NOTE. Is often preceded by the term electrophoretic or electrolytic to indicate mobility in a specific system.
molal. See molality.
Term | Symbol | Unit |
molality | m | mol kg^{-1} |
Amount-of-substance of a solute substance (component) (in a solution) divided by the mass of the solvent (11).
NOTES
molar. Modifier used to denote divided by amount-of-substance (7).
NOTE. Use of the term molar to denote a unit of amount-of-substance concentration is discouraged.
molar absorptivity. See absorption coefficent (molar).
molar absorption coefficient. See absorption coefficent (molar).
molar concentration. See substance concentration.
Term | Symbol | Unit |
molar conductivity | [[Lambda]] S | m^{2} mol^{-1} |
Conductivity of an electrolyte divided by its substance concentration (11).
NOTES
Term | Symbol | Unit |
(molar) gas constant | R | J K^{-1} mol^{-1} |
Universal constant of proportionality in the ideal gas law (11).
NOTE. The gas constant is equal to the product of the Avogadro constant and the Boltzmann constant:
R = Lk = 8,314 510 (70) J K^{-1} mol^{-1}
Term | Symbol | Unit |
molar heat capacity | C_{m} | J mol^{-1} K^{-1} |
Heat capacity divided by amount-of-substance (12).
NOTE. See heat capacity.
Term | Symbol | Unit |
molar mass | M | kg mol^{-1} |
Mass of a component divided by its amount-of-substance (12).
NOTE. The term component is recommended for clinical chemistry (2), ISO uses substance.
Term | Symbol | Unit |
molar volume | V_{m} | m^{3} mol^{-1} |
Volume of a component divided by its amount-of-substance (12).
NOTE. The term component is recommended for clinical chemistry (2). ISO uses substance.
molarity. See substance concentration.
NOTE. Use of the term molarity to describe the amount-of-substance concentration is not recommended.
Term | Symbol |
mole | mol |
Base unit of the SI for amount-of-substance, equal to the amount-of-substance of a system which contains as many elementary entities as there are atoms in 0,012 kilogram of carbon 12 (13).
NOTE. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles.
mole fraction. See substance fraction.
molecular weight. See relative molecular mass.
Term | Symbol | Unit |
moment of inertia | I | m^{2} kg |
Sum (or integral) of the products of the masses of the elements of a body rotating about an axis and the squares of their distances from the axis (10).
Term | Symbol |
nano | n |
Prefix used with SI units to denote 10^{-9} (13).
Term | Symbol |
newton | N |
SI unit for force, equal to the force required to accelerate a body with the mass one kilogram by one metre per second per second (13).
NOTE. 1 N = m kg s^{-2}.
Term | Symbol | Unit |
number concentration | C_{N} | m^{-3} |
Number of defined particles, or elementary entities, of a component in a system divided by the volume of that system (2).
NOTES
Term | Symbol | Unit |
number content | N_{B}/m | kg^{-1} |
Number of defined particles, or elementary entities, of a component in a system divided by the mass of that system (2).
NOTES
Term | Symbol | Unit |
number fraction | x | 1 |
Number of defined particles, or elementary entities of a specified component divided by the total number of defined particles in the system (2).
NOTES
Term | Symbol | Unit |
number flow rate | q_{N} | s^{-1} |
Number of defined particles, or elementary entities of a defined component, crossing a cross section divided by the time.
NOTES
Term | Symbol | Unit |
number of entities | N | 1 |
Number of molecules or other elementary entities in a system (12).
numerical value (of a quantity). Quotient of the value of a quantity and the unit used in its expression (14).
NOTE. See value (of a quantity).
Term | Symbol |
ohm | [[Omega]] |
SI unit for electric resistance, equal to the electric resistance between two points of a conductor when a constant potential difference of 1 V, applied to these points, produces in the conductor a current of 1 A, the conductor not being the seat of any electromotive force (13).
NOTE. 1 [[Omega]] = V A^{-1} = m^{2} kg s^{-3} A^{-2}
optical density. See absorbance.
NOTE. Use of the term optical density to denote absorbance is deprecated by IUPAC.
Term | Symbol | Unit |
osmolality | m | mol kg^{-1} |
Quotient of the negative natural logarithm of the rational activity of water and the molar mass of water (4).
osmolarity. See osmotic concentration.
Term | Symbol | Unit |
osmotic coefficient | [[phi]] | 1 |
Quotient of the osmolality of a solute (component) and the sum of the molalities of all the solutes in the solution (4).
Term | Symbol | Unit |
osmotic concentration | c | mol m^{-3} |
Product of the osmolality and the mass density of water (4).
NOTES
Term | Symbol | Unit |
osmotic pressure | [[Pi]] | Pa |
Pressure difference between the solution and the pure solvent which provides the same chemical potential of the solvent in the solution and in the pure solvent (4).
NOTE. Also defined as the excess pressure required to maintain osmotic equilibrium between a solution and the pure solvent separated by a membrane permeable only to the solvent (12).
Term | Symbol | Unit |
partial mass density | [[rho]]_{B} | kg m^{-3} |
Change in mass due to addition of a small amount of component to a system divided by the change in volume of the system (10).
NOTE. The systematic name is partial volumic mass.
Term | Symbol | Unit |
partial pressure | p_{B} | Pa |
Product of the amount-of-substance fraction of a gaseous component and the pressure of the gaseous system (12).
Term | Symbol | Unit |
partial specific volume | v_{B} | m^{3} kg^{-1} |
Change in volume of a system when a small amount of component is added divided by the mass of thae added component (10).
NOTE. The systematic name is partial massic volume.
partition coefficient. See distribution constant.
Term | Symbol |
pascal | Pa |
SI unit for pressure, equal to of one newton acting perpendicular to a surface of area per square metre (13).
NOTE. 1 Pa = 1 N m^{-2} = 1 kg m^{-1} s^{-2}
Term | Symbol | Unit |
period | T | s |
A time divided by the number of regularly repeating events during that time (12).
NOTE. It is the time taken to complete one cycle of a defined event.
Term | Symbol |
peta | P |
Prefix used with SI units to denote 10^{15} (13).
pH. Quantity of dimension one used to express the hydrogen ion concentration of dilute aqueous solutions, where:
pH » -lg[[[gamma]]+/-c(H^{+})/mol L^{-1}] +/- 0,02 (11).
NOTES
Term | Symbol |
pico | p |
Prefix used with SI units to denote 10^{-12} (13).
Term | Symbol | Unit |
plane angle | [[alpha]], [[beta]], [[gamma]], J, .... | rad |
Ratio of the arc cut out in a circle with its centre at that point to the radius of the circle (12).
NOTES
Term | Symbol |
poise | P |
Non SI unit for viscosity, equal to 0,1 Pa·s (13).
NOTE. The poise is a unit of the CGS unit system, and its use is discouraged.
Term | Symbol | Unit |
power | P | W |
Rate of energy transfer (11).
NOTES
Term | Symbol | Unit |
pressure | p | Pa |
Force divided by the area over which the force is acting (12).
quantity. Attribute of a phenomenon, body or substance that may be distinguished qualitatively and determined quantitatively (14).
NOTES
quantity of dimension one; dimensionless quantity. Quantity in the dimensional expression of which all the exponents of the dimensions of the base quantities are zero (14).
Term | Symbol |
rad | rad |
Non SI unit for absorbed dose of ionizing radiation, equal to one centigray (13).
NOTE. Approved by the CIPM for temporary use with the SI until considered no longer necessary.
Term | Symbol |
radian | rad |
SI unit for plane angle, equal to the angle between two radii of a circle which cut off on the circumference an arc equal in length to the radius (13).
NOTES
Term | Symbol | Unit |
radiant energy | Q | J |
Energy propagated as electromagnetic radiation (5).
Term | Symbol | Unit |
radiant exitance | M | W m^{-2} |
Radiant power emitted by an element of surface at uniform temperature divided by the surface area of that element (5).
radiant flux. See radiant power.
Term | Symbol | Unit |
radiant power | P | W |
Amount of radiant energy transferred to or from a defined system divided by the time interval (5).
NOTE. Also called radiant (energy) flux.
radioactivity. See activity (radionuclide).
Term | Symbol | Unit |
rate | x | s^{-1} |
Derived quantity in which time is a denominator quantity (7).
Term | Symbol | Unit |
rate coefficient | k | s^{-1} |
Number fraction of particles of a component in a medium passing a given position in the direction of an applied force divided by time (10).
NOTE. The applied force may be gravitational acceleration in column chromatography, rotational acceleration in centrifugation, electromotive force in electrophoresis.
Term | Symbol | Unit |
rate constant | k | varies |
Proportionality coefficient in a chemical reaction rate equation (11).
Term | Symbol | Unit |
rate of conversion | [[xi]] | mol s^{-1} |
Change in the extent of a reaction over a time interval divided by that time interval (11).
NOTE. See extent of reaction.
Term | Symbol | Unit |
rate of reaction | v | mol m^{-3} s^{-1} |
Rate of conversion of a (given) reaction divided by the volume of the system (11).
NOTE. See extent of reaction.
Term | Unit |
ratio | 1 |
Quotient of quantities of the same kind for different components within the same system (7).
Term | Symbol | Unit |
reflectance | [[rho]] | 1 |
Radiant power specularly reflected from the surfaces of a system divided by the incident radiant power (5).
NOTES
Term | Symbol | Unit |
refractive index | n | 1 |
Quotient of the speed in vacuum of electromagnetic radiation at a given spectral position and its speed in a given medium (5).
NOTE. The medium must be non absorbing, i.e. not absorb the electromagnetic radiation at the spectral position.
relative. Quotient of quantities having the same kind-of-quantity in different systems (7).
NOTES
Term | Symbol | Unit |
(relative) activity | a | 1 |
Number defined by a_{B} = exp(µ_{B}-µ_{B}-/RT) when a component, B, is in a mixture of components (11), where:
µ_{B} = chemical potential of the component
µ_{B}- = standard chemical potential of the component
R = molar gas constant
T = thermodynamic temperature
NOTES
Term | Symbol | Unit |
relative atomic mass | A_{r} | 1 |
Ratio of the average mass per atom of an element to 1/12 of the mass of an atom of nuclide ^{12}C (12).
NOTE. Also known as atomic weight.
Term | Symbol | Unit |
relative density | d | 1 |
Quotient of the density of a substance and the density of a reference substance under specified conditions (12).
NOTES
Term | Symbol | Unit |
relative molecular mass | M_{r} | 1 |
Ratio of the average mass per molecule of a compound to 1/12 of the mass of an atom of nuclide ^{12}C (12).
NOTE. Also known as molecular weight.
Term | Symbol |
rem | rem |
Non SI unit for dose equivalent, equal to one centisievert (13).
NOTES
repetency. wavenumber.
Term | Symbol | Unit |
resistance | R | [[Omega]] |
Electric potential difference divided by the electric current when there is no electromotive force in a conductor (12).
Term | Symbol | Unit |
resistivity | [[rho]] | [[Omega]] m |
Electric field strength divided by the current density when there is no electromotive force in a conductor (12).
Term | Symbol |
revolutions per minute | rpm |
Non SI unit for rotational frequency (10).
NOTE. See rotational frequency.
Term | Symbol |
röntgen | R |
Non SI unit used to express exposure to ionizing radiation (13).
NOTES
Term | Symbol | Unit |
rotational frequency | f_{rot} | Hz |
Number of rotations divided by time (10).
NOTES
Term | Symbol | Unit |
saturation fraction | s_{B} | 1 |
Amount-of-substance of a component (solute) in a solution divided by the amount-of-substance of the component when it is saturating the system at constant temperature and pressure (4).
NOTE. Also referred to simply as saturation, for example oxygen saturation.
Term | Symbol |
second (of arc) | " |
Non SI unit for plane angle, equal to ([[pi]]/648 000) rad (13).
NOTE. Because of its importance and wide use, the CIPM approved use of the second (of arc) with SI units.
Term | Symbol |
second (of time) | s |
Base unit of the SI for time, equal to the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom (13).
Term | Symbol | Unit |
sedimentation coefficient | s_{B} | s |
Reciprocal of the rate coefficient of a suspended component in a fluid passing a given position in the direction of gravitational or centrifugal acceleration (10).
NOTES
Term | Symbol | Unit |
sedimentation velocity | v_{B} | m s^{-1} |
Velocity of a component in a fluid relative to the fluid in the direction of gravitational or centrifugal acceleration (10).
NOTES
Term | Symbol |
siemens | S |
SI unit for electric conductance, equal to the conductance between two points of a conductor having a resistance of 1 [[Omega]] (13).
NOTE. 1 S = 1 A V^{-1} = 1 m^{-2} kg^{-1} s^{3} A^{2}.
Term | Symbol |
sievert | Sv |
SI unit for dose equivalent of absorbed radiant energy (13).
NOTES
Term | Symbol |
solid angle | sr |
Ratio of the area cut out on a spherical surface (with its centre at the apex of a cone) to the square of the radius of the sphere (12).
NOTE. See also steradian.
specific. Modifier used to denote divided by mass (12).
EXAMPLES. specific activity, specific heat.
NOTE. Use of the term massic instead of specific is recommended (7), for example, massic activity, massic heat, etc.
Term | Symbol | Unit |
specific activity | a | Bq kg^{-1} |
Activity of a sample divided by its mass (12).
NOTES
specific conductance. See conductivity.
Term | Symbol | Unit |
specific heat capacity | c | J kg^{-1} K^{-1} |
Heat capacity divided by mass (12).
NOTE. See heat capacity.
Term | Symbol | Unit |
specific volume | v | m^{3} kg^{-1} |
Volume of a substance divided by its mass (12).
NOTES
speed. See velocity.
standard atmosphere. See atmosphere.
Term | Symbol |
steradian | sr |
SI unit for solid angle, equal to the solid angle extending from the centre of a sphere to span an area on its surface equal to the square of the radius (13).
NOTE. The solid angle is a quantity of dimension one.
Term | Symbol |
stokes | St |
Unit for kinematic viscosity in the CGS system of units (13).
NOTES
Term | Symbol | Unit |
stoichiometric number | [[nu]] | 1 |
Number or simple fraction for a substance (component) occurring in the expression for a chemical reaction (12).
NOTES
Term | Symbol | Unit |
substance concentration | c | mol m^{-3} |
Amount-of-substance of a component divided by the volume of the system (2).
NOTES
Term | Symbol | Unit |
substance content | n/m | mol kg^{-1} |
Amount-of-substance of a component divided by the mass of the system (2).
NOTES
Term | Symbol | Unit |
substance fraction | x | 1 |
Ratio of the amount-of-substance of the component to the total amount-of-substance in the system containing the component (2).
NOTES
Term | Unit |
substance flow rate | mol s^{-1} |
Amount-of-substance of a component crossing a surface divided by the time (12).
NOTE. For clinical chemistry the term component is recommended (2). ISO uses substance.
Term | Symbol | Unit |
surface density | [[rho]]_{S} | kg m^{-2} |
Mass divided by area (12).
NOTE. The systematic name is areic mass.
Term | Symbol | Unit |
surface tension | [[gamma]] | N m^{-1} |
Force perpendicular to a line element in a surface divided by the length of the line element (12).
symbol (in quantities and units). Conventional sign designating a quantity or a unit of measurement (12).
NOTES
system. Arbitrarily defined part of the universe, regardless of form or size (1).
EXAMPLES. patient, patient plasma, patient urine.
system of units (of measurement). Set of base units, together with derived units, defined in accordance with given rules, for a given system of quantities (14).
EXAMPLE. Système International d'Unités.
Système International d'Unités (SI). Coherent system of units adopted and recommended by the Conférence Général de Poids et Mesures (CGPM) (14).
NOTE. At present, the SI is based on the following seven base units (13):
temperature. See thermodynamic temperature.
Term | Symbol |
tera | T |
Prefix used with SI units to denote 10^{12} (13).
Term | Symbol |
thermochemical calorie | cal_{th} |
Non SI unit for energy, equal to 4,184 J (13).
NOTES
Term | Symbol | Unit |
thermodynamic temperature | T | K |
Base quantity of the International System of Units (12).
NOTE. See Système International d'Unités.
Term | Symbol | Unit |
time | t | s |
Base quantity of the International System of Units (12).
NOTE. See Système International d'Unités.
Term | Symbol |
torr | torr |
Non SI unit for pressure (11).
NOTES
transmission. See transmittance.
Term | Symbol | Unit |
transmittance | [[tau]] | 1 |
Radiant power transmitted by a system in the direction of a parallel beam, divided by the incident radiant power (5).
NOTES
true value (of a quantity). Value consistent with the definition of a given particular quantity (14).
NOTES
Term | Symbol | Unit |
unified atomic mass unit | u | kg |
Non SI unit for mass, equal to 1/12 of the rest mass of a neutral atom of the nuclide ^{12}C in its nuclear and atomic glound state (11).
NOTES
unit (of measurement). Particular quantity, defined and adopted by convention, with which other quantities of the same kind are compared in order to express their magnitudes relative to that quantity (14).
value (of a quantity). Magnitude of a particular quantity generally expressed as a unit of measurement multiplied by a number (14).
Term | Symbol | Unit |
velocity | v | m s^{-1} |
Distance travelled divided by time of travel (10).
Term | Symbol | Unit |
viscosity; dynamic viscosity | [[eta]] | Pa s |
Constant of proportionality for shear stress, [[tau]]_{xz}, in a fluid moving with a velocity gradient dv_{x}/dz perpendicular to the plane of shear (10).
NOTE. [[tau]]_{x,z} = [[eta]](dv_{x}/dz)
Term | Symbol |
volt | V |
SI unit for electric potential, equal to the potential difference between two points of a conducting wire carrying a constant current of 1 A, when the power dissipated between these points is equal to 1 W (13).
NOTE. 1 V = 1 W A^{-1} = 1 m^{2} kg s^{-3} A^{-1}.
Term | Symbol | Unit |
volume | V | m^{3} |
V = ||| dx dy dz (12).
NOTE. In clinical chemistry the litre, symbol l or L, is the recommended unit for volume (2).
Term | Symbol | Unit |
volume flow rate | q_{v} | m^{3} s^{-1} |
Volume of a component crossing a surface divided by the time (12).
NOTE. For clinical chemistry the term component is recommended (2), ISO uses substance.
Term | Symbol | Unit |
volume fraction | [[phi]] | 1 |
Quotient of the volume of a component and the total volume of the system containing the component (12).
NOTES
volume rate. See clearance.
volumic. Modifier used to denote divided by volume of the system (7).
Term | Symbol | Unit |
volumic mass | [[rho]] | kg m^{-3} |
The volumic mass of a substance is its mass divided by its volume (7).
NOTES
Term | Symbol |
watt | W |
The watt is the SI unit for power, equal to the power which in 1 s give rise to energy of 1 J (13).
NOTE. 1 W = 1 J s^{-1} = 1 m^{2} kg s^{-3}.
Term | Symbol | Unit |
wavelength | [[lambda]] | m |
Distance in the direction of propagation of a regular wave divided by the number of cycles of the wave in that distance (5).
Term | Unit |
wavenumber (in a vacuum) | J m^{-1} |
Number of cycles of a regular wave in a given distance divided by that distance (5).
NOTE. The systematic name is repetency.
Term | Symbol |
weber | Wb |
The weber is the SI unit for magnetic flux, equal to the magnetic flux which, linking a circuit of one turn, would produce in it an electromotive force of 1 V if it were reduced to zero at a uniform rate of 1 s (13).
NOTE. 1 Wb = 1 V s = 1 m^{2} kg s^{-2} A^{-1}.
Term | Symbol | Unit |
weight | G | N |
Force which when applied to a body in a specified reference system would give it an acceleration equal to the local acceleration of free fall in that reference system (12).
NOTE. The term weight is often used as a synonym for mass, but this usage is discouraged.
Term | Symbol | Unit |
work | W | J |
Force multiplied by the displacement in the direction of the force (12).
NOTE. See also joule.
Term | Symbol |
yocto | y |
Prefix used with the SI to denote 10^{-24} (13).
Term | Symbol |
yotta | Y |
Prefix used with the SI to denote 10^{24} (13).
Term | Symbol |
zepto | z |
Prefix used with the SI to denote 10^{-21} (13).
zeta potential. See electrokinetic potential.
Term | Symbol |
zetta | Z |
Prefix used with the SI to denote 10^{21} (13).
Chairmen: H. P. Lehmann (USA); H. Olesen (Denmark),
Titular Members: D. R. Bangham (UK); L. F. Bertello (Argentina); G. Férard (France); X. Fuentes-Arderiu (Spain); J. G. Hill (Canada); M. Lauritzen (Denmark); P. Storring (UK),
Associate Members: S. J. Bryant (Australia); D. J. Cambell (Canada); J. Kratochvila (Czech Republic); C. Onkelinx (Belgium); O Siggaard-Andersen (Denmark); P. Soares de Araujo (Brazil); C-H. de Verdier (Sweden); B. F. Visser (Netherlands); U. Worsaae (Denmark); R. Zender (Switzerland).
H. Peter Lehmann, Ph.D., Dept. of Patholgy, Louisiana State Univ. Med. Center, 1901 Perdido Street, New Orleans, Louisiana 70112, USA.
X. Fuentes-Arderiu, Ph.D., Servei de Bioquímica Clínica, Ciutat Sanitària i Universitària de Bellvitge, Feixa Llarga s/n, 08907 L'Hospitalet de Llobregat, Barcelona, Spain.
Louis F. Bertello, Prof., Perù 420, 1641 Acassuso, R. Argentina.