Metric units are units based on the metre, gram or second and decimal (power of ten) multiples or sub-multiples of these. The most widely used examples are the units of the International System of Units (SI). By extension they include units of

electromagnetism In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions o ...

from the CGS and SI units systems, and other units for which use of

SI prefix The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. ...

es has become the norm. Other unit systems using metric units include: *

International System of Electrical and Magnetic Units The International System of Electrical and Magnetic Units is an obsolete system of units used for measuring electrical and magnetic quantities. It was proposed as a system of practical international units by unanimous recommendation at the Internat ...

* Metre–tonne–second (MTS) system of units *

MKS system of units The MKS system of units is a physical system of measurement that uses the metre, kilogram, and second (MKS) as base units. It forms the base of the International System of Units (SI), though SI has since been redefined by different fundamental ...

(metre, kilogram, second)

Metric units that are part of the SI

The first group of metric units are those that are at present defined as units within the International System of Units (SI). In its most restrictive interpretation, this is what may be meant when the term ''metric unit'' is used. The SI defines 30 named units and associated symbols: * The unit

one 1 (one, unit, unity) is a number representing a single or the only entity. 1 is also a numerical digit and represents a single unit of counting or measurement. For example, a line segment of ''unit length'' is a line segment of length 1. I ...

(1) is the unit of a quantity of dimension one. * The second (s) is the unit of

time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, t ...

. * The

metre The metre ( British spelling) or meter ( American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its p ...

(m) is the unit of

length Length is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance. In most systems of measurement a base unit for length is chosen, from which all other units are derived. In the Inte ...

. * The

kilogram The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially ...

(kg) is the unit of

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different element ...

. * The

ampere The ampere (, ; symbol: A), often Clipping (morphology), shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One amp ...

(A) is the unit of

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The movin ...

. * The

kelvin The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and ph ...

(K) is the unit of

thermodynamic temperature Thermodynamic temperature is a quantity defined in thermodynamics as distinct from kinetic theory or statistical mechanics. Historically, thermodynamic temperature was defined by Kelvin in terms of a macroscopic relation between thermodynamic ...

. * The mole (mol) is the unit of

amount of substance In chemistry, the amount of substance ''n'' in a given sample of matter is defined as the quantity or number of discrete atomic-scale particles in it divided by the Avogadro constant ''N''A. The particles or entities may be molecules, atoms, io ...

. * The

candela The candela ( or ; symbol: cd) is the unit of luminous intensity in the International System of Units (SI). It measures luminous power per unit solid angle emitted by a light source in a particular direction. Luminous intensity is analogous t ...

(cd) is the unit of luminous intensity. * The

hertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one her ...

(Hz) is equal to one reciprocal second (). * The

radian The radian, denoted by the symbol rad, is the unit of angle in the International System of Units (SI) and is the standard unit of angular measure used in many areas of mathematics. The unit was formerly an SI supplementary unit (before tha ...

(rad) is equal to one (). * The

steradian The steradian (symbol: sr) or square radian is the unit of solid angle in the International System of Units (SI). It is used in three-dimensional geometry, and is analogous to the radian, which quantifies planar angles. Whereas an angle in radi ...

(sr) is equal to one (). * The newton (N) is equal to one kilogram-metre per second squared (). * The pascal (Pa) is equal to one newton per square metre (). * The

joule The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applie ...

(J) is equal to one newton-metre (). * The

watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wa ...

(W) is equal to one joule per second (). * The

coulomb The coulomb (symbol: C) is the unit of electric charge in the International System of Units (SI). In the present version of the SI it is equal to the electric charge delivered by a 1 ampere constant current in 1 second and to elementary ch ...

volt The volt (symbol: V) is the unit of electric potential, electric potential difference ( voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827). D ...

(V) is equal to one joule per coulomb (). * The

weber Weber (, or ; German: ) is a surname of German origin, derived from the noun meaning " weaver". In some cases, following migration to English-speaking countries, it has been anglicised to the English surname 'Webber' or even 'Weaver'. Notable pe ...

(Wb) is equal to one volt-second (). * The tesla (T) is equal to one weber per square metre (). * The

farad The farad (symbol: F) is the unit of electrical capacitance, the ability of a body to store an electrical charge, in the International System of Units (SI). It is named after the English physicist Michael Faraday (1791–1867). In SI base unit ...

(F) is equal to one coulomb per volt (). * The ohm (Ω) is equal to one volt per ampere (). * The siemens (S) is equal to one ampere per volt (). * The henry (H) is equal to one volt-second per ampere (). * The degree Celsius (°C) is equal to one kelvin (). * The lumen (lm) is equal to one candela-steradian (). * The

lux The lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, in the International System of Units (SI). It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the ...

(lx) is equal to one lumen per square metre (). * The becquerel (Bq) is equal to one reciprocal second (). * The

gray Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed ...

(Gy) is equal to one joule per kilogram (). * The sievert (Sv) is equal to one joule per kilogram (). * The katal (kat) is equal to one mole per second (). There are twenty-four

metric prefix A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The pr ...

es that can be combined with any of these units except one (1) and kilogram (kg) to form further units of the SI. For mass, the same prefixes are applied to the gram (g) instead of the kilogram.

Metric units that are not part of the SI

There are several metric systems, most of which have become disused or are still used in only niche disciplines. Systems are listed with named units that are associated with them.

CGS

The

centimetre–gram–second system of units The centimetre–gram–second system of units (abbreviated CGS or cgs) is a variant of the metric system based on the centimetre as the unit of length, the gram as the unit of mass, and the second as the unit of time. All CGS mechanical un ...

(CGS) is based on three base units: centimetre, gram and second. Its subsystems ( CGS-ESU, CGS-EMU and CGS-Gaussian) have different defining equations for their systems of quantities for defining electromagnetic quantities and hence the associated units, with CGS-Gaussian units being selected from each of the other two subsystems. The CGS-to-SI correspondence of electromagnetic units as given was exact prior to the

2019 redefinition of the SI base units In 2019, four of the seven SI base units specified in the International System of Quantities were redefined in terms of natural physical constants, rather than human artifacts such as the standard kilogram. Effective 20 May 2019, the 144th ...

, until which the magnetic constant ''μ''₀ was defined as . As from the redefinition, ''μ''₀ has an inexactly known value when expressed in SI units, with the exactness of the electromagnetic unit correspondence given here being affected accordingly.

CGS nonelectromagnetic units

* The kayser (K) is a unit of wavenumber equal to (). * The gal (Gal) is a unit of

acceleration In mechanics, acceleration is the rate of change of the velocity of an object with respect to time. Accelerations are vector quantities (in that they have magnitude and direction). The orientation of an object's acceleration is given by ...

equal to . * The dyne (dyn) is a unit of

force In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a ...

equal to (). * The barye (Ba) is a unit of

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...

equal to (). * The erg (erg) is a unit of

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...

equal to (). * The

poise Poise may mean: * Poise (unit), a measure of viscosity * A concept similar to gracefulness * Ferdinand Poise image:Ferdinand Poise 1892.jpg, Jean Alexandre Ferdinand Poise (3 June 1828 – 13 May 1892) was a French composer, mainly of opéra ...

(P) is a unit of

dynamic viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the inte ...

equal to (). * The stokes (St) is a unit of

kinematic viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the intern ...

equal to (). * The stilb (sb) is a unit of luminance equal to (). * The phot (ph) is a unit of

illuminance In photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightn ...

equal to (). * The rayl is a unit of specific acoustic impedance, equal to 1 dyn⋅s⋅cm⁻³.

CGS-ESU electromagnetic units

* The statwatt (statW) is a unit of power equal to , which is equal to . * The statcoulomb (statC) or franklin (Fr) is a unit of

electric charge Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respecti ...

equal to , corresponding to ~. * The

statampere The statampere (statA) is the derived electromagnetic unit of electric current in the CGS-ESU (electrostatic cgs) and Gaussian systems of units. One statampere corresponds to / ampere ≈ in the SI system of units. The name ''statampere'' is ...

(statA) is a unit of

equal to , corresponding to ~. * The statvolt (statV) is a unit of electric potential difference equal to , corresponding to . * The

statohm The statohm is the unit of electrical resistance in the electrostatic system of units which was part of the CGS system of units based upon the centimetre, gram and second. The static units in that system were related to the equivalent electromagn ...

is a unit of

electric resistance The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallel ...

equal to , corresponding to ~. * The statsiemens or

statmho The statmho is the unit of electrical conductance in the electrostatic system of units (ESU), an extension of the centimeter-gram-second (CGS) system to cover electrical units. It is sometimes called the statsiemens, with symbol statS. Conversio ...

is a unit of electric conductance equal to , corresponding to ~. * The stathenry is a unit of electric inductance equal to , corresponding to ~. * The

statfarad The farad (symbol: F) is the unit of electrical capacitance, the ability of a body to store an electrical charge, in the International System of Units (SI). It is named after the English physicist Michael Faraday (1791–1867). In SI base units ...

(statF) is a unit of electric capacitance equal to , corresponding to ~. * The statdaraf (statD) is a unit of electric elastance equal to 1/statF. * The statweber is a unit of magnetic flux, corresponding to . * The stattesla is a unit of magnetic flux density equal to , corresponding to .

CGS-EMU electromagnetic units

* The abwatt (abW) is a unit of power equal to , which is equal to . * The abcoulomb (abC) is a unit of

equal to , corresponding to . * The abampere (abA) or biot (Bi) is a unit of

, corresponding to . * The abvolt (abV) is a unit of electric potential difference, corresponding to . * The abohm (abΩ) is a unit of

, corresponding to . * The abmho is a unit of electric conductance, corresponding to . * The abhenry is a unit of electric inductance, corresponding to . * The abfarad (abF) is a unit of electric capacitance, corresponding to . * The

gilbert Gilbert may refer to: People and fictional characters *Gilbert (given name), including a list of people and fictional characters *Gilbert (surname), including a list of people Places Australia * Gilbert River (Queensland) * Gilbert River (South A ...

(Gb) is a unit of magnetomotive force equal to one biot-turn, corresponding to (10/4π) A = . * The oersted (Oe) is a unit of magnetic field strength equal to , corresponding to (1000/4π) A/m = . * The

maxwell Maxwell may refer to: People * Maxwell (surname), including a list of people and fictional characters with the name ** James Clerk Maxwell, mathematician and physicist * Justice Maxwell (disambiguation) * Maxwell baronets, in the Baronetage o ...

(Mx) is a unit of magnetic flux, corresponding to . * The

gauss Johann Carl Friedrich Gauss (; german: Gauß ; la, Carolus Fridericus Gauss; 30 April 177723 February 1855) was a German mathematician and physicist who made significant contributions to many fields in mathematics and science. Sometimes refer ...

(G) is a unit of magnetic flux density, corresponding to .

CGS-Gaussian electromagnetic units

* The franklin (Fr) is a unit of

equal to , corresponding to ~. * The oersted (Oe) is a unit of magnetic field strength equal to , corresponding to ~. * The

(Mx) is a unit of magnetic flux, corresponding to . * The

(G) is a unit of magnetic flux density, corresponding to .

MTS

* The

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...

(t) is a unit of

equal to . * The sthène (sn) is a unit of

equal to . * The

pièze The pièze () is the unit of pressure in the metre–tonne–second system of units (mts system), used, e.g., in the former Soviet Union 1933–1955. It is defined as one sthène The sthène (; symbol sn), sometimes spelled (or misspelled) sthéne ...

(pz) is a unit of

equal to .

MKSA

* The

cycle per second The cycle per second is a once-common English name for the unit of frequency now known as the hertz (Hz). The plural form was typically used, often written cycles per second, cycles/second, c.p.s., c/s, or, ambiguously, just cycles (Cy./Cyc.). T ...

(cps or cyc/s) is a unit of

frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from '' angular frequency''. Frequency is measured in hertz (Hz) which is ...

equal to . * The MKS rayl is a unit of acoustic impedance equal to . * The

mho The siemens (symbol: S) is the unit of electric conductance, electric susceptance, and electric admittance in the International System of Units (SI). Conductance, susceptance, and admittance are the reciprocals of resistance, reactance, and ...

(℧) is a unit of electric conductance equal to .

MKpS units

* The kilogram-force (kgf), also kilopond (kp), is a unit of

(). * The hyl is a unit of

equal to (). * The poncelet (p) is a unit of power equal to (). * The

technical atmosphere Technical may refer to: * Technical (vehicle), an improvised fighting vehicle * Technical analysis, a discipline for forecasting the future direction of prices through the study of past market data * Technical drawing, showing how something is c ...

(at) is a (non-coherent) unit of

equal to ().

Other metric units

Length

* The fermi is a unit of distance used in

nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies the ...

equal to . * The

angstrom The angstromEntry "angstrom" in the Oxford online dictionary. Retrieved on 2019-03-02 from https://en.oxforddictionaries.com/definition/angstrom.Entry "angstrom" in the Merriam-Webster online dictionary. Retrieved on 2019-03-02 from https://www.m ...

(symbol Å) is a unit of distance used in chemistry and atomic physics equal to . * The

micron The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer ( American spelling), also commonly known as a micron, is a unit of length in the International System of Un ...

(μ) is a unit of distance equal to one

micrometre The micrometre ( international spelling as used by the International Bureau of Weights and Measures; SI symbol: μm) or micrometer ( American spelling), also commonly known as a micron, is a unit of length in the International System of ...

(). * The basic module (M) is a unit of distance equal to one hundred millimetres (). * The myriametre (mym) is a unit of distance equal to ten kilometres (). * The

hebdometre Hebdo- (symbol H) is an obsolete decimal metric prefix equal to 107. It is derived from the Greek ''hebdοmos'' ( el, ἕβδομος) meaning ''seventh''. The definition of one ''hebdomometre'' or ''hebdometre'' as was originally proposed by ...

is a unit of distance equal to ten megametres (). * The spat (S) is a unit of distance equal to one terametre ().

Area

* The shed is a unit of area used in nuclear physics equal to 10⁻²⁴

barn A barn is an agricultural building usually on farms and used for various purposes. In North America, a barn refers to structures that house livestock, including cattle and horses, as well as equipment and fodder, and often grain.Allen ...

s (100 rm² = 10⁻⁵² m²). * The

outhouse An outhouse is a small structure, separate from a main building, which covers a toilet. This is typically either a pit latrine or a bucket toilet, but other forms of dry (non-flushing) toilets may be encountered. The term may also be used ...

is a unit of area used in nuclear physics equal to 10⁻⁶ barns (100 am² = 10⁻³⁴ m²). * The

(b) is a unit of area used in nuclear physics equal to one hundred femtometres squared (100 fm² = 10⁻²⁸ m²). * The

are Are commonly refers to: * Are (unit), a unit of area equal to 100 m2 Are, ARE or Åre may also refer to: Places * Åre, a locality in Sweden * Åre Municipality, a municipality in Sweden **Åre ski resort in Sweden * Are Parish, a municipa ...

(a) is a unit of area equal to . * The decare (daa) is a unit of area equal to . * The

hectare The hectare (; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100- metre sides (1 hm2), or 10,000 m2, and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is ...

(ha) is a unit of area equal to .

Volume

* The

lambda Lambda (}, ''lám(b)da'') is the 11th letter of the Greek alphabet, representing the voiced alveolar lateral approximant . In the system of Greek numerals, lambda has a value of 30. Lambda is derived from the Phoenician Lamed . Lambda gave ris ...

(λ) is a unit of volume equal to one cubic millimetre (1 mm³). * The

litre The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3 ...

(symbol l or L) is a unit of volume equal to one cubic decimetre (1 dm³). * The stere (st) is a unit of volume equal to .

Reciprocal length

* The dioptre is a unit of optical power equal to one reciprocal metre ().

Time

* The svedberg (S or Sv) is a unit of time used in chemistry equal to one hundred femtoseconds (). * The shake is a unit of time used in nuclear physics equal to ten

nanosecond A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or 10 seconds. The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit ...

s (). * The

sigma Sigma (; uppercase Σ, lowercase σ, lowercase in word-final position ς; grc-gre, σίγμα) is the eighteenth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 200. In general mathematics, uppercase Σ is used ...

is a unit of time equal to one

microsecond A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or ) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available. A microsecond is equal to 100 ...

(). * The jiffy is sometimes used to mean a unit of time of .

Reciprocal time

* The fresnel is a unit of

equal to .

Reciprocal time squared

* The eotvos (E) is a unit of gravitational gradient equal to ().

Speed

* The

benz Benz, an old Germanic clan name dating to the fifth century (related to "bear", "war banner", "gau", or a "land by a waterway") also used in German () as an alternative for names such as Berthold, Bernhard, or Benedict, may refer to: People Sur ...

is a unit of

speed In everyday use and in kinematics, the speed (commonly referred to as ''v'') of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a scalar quantity ...

equal to one metre per second (1 m/s).

Acceleration

* The leo is a unit of acceleration equal to .

Flow rate

* The sverdrup (Sv) is a unit of volume flow rate equal to one million metres cubed per second (10⁶ m³/s).Aldersey-Williams, 2016
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Mass

* The undecimogramme is a unit of

equal to ten picograms (10 pg). * The gamma (γ) is a unit of

equal to one microgram (1 μg). * The gravet is a unit of

equal to one gram (1 g). * The

grave A grave is a location where a dead body (typically that of a human, although sometimes that of an animal) is buried or interred after a funeral. Graves are usually located in special areas set aside for the purpose of burial, such as grave ...

is a unit of

equal to one kilogram (1 kg). * The

bar Bar or BAR may refer to: Food and drink * Bar (establishment), selling alcoholic beverages * Candy bar * Chocolate bar Science and technology * Bar (river morphology), a deposit of sediment * Bar (tropical cyclone), a layer of cloud * Bar (un ...

is a unit of

equal to one megagram (1 Mg).

Linear mass density

* The tex (tex) is a unit of linear mass density equal to one gram per kilometre (1 g/km). * The number metric (Nm) is equal to 1000 metres per kilogram (1 km/kg).

Pressure

* The metre sea water (msw) is a unit of

defined as 0.1

, which is equal to . * The bar (bar) is a unit of

equal to .

Energy

* The

foe Friends of the Earth International (FoEI) is an international network of environmental organizations in 73 countries. The organization was founded in 1969 in San Francisco by David Brower, Donald Aitken and Gary Soucie after Brower's split w ...

is a unit of

equal to ().

Viscosity

* The poiseuille is a unit of

equal to one pascal-second ().

Electrical

* The Siemens mercury unit is a unit of

, corresponding to ~. * The gamma (γ) a unit of magnetic flux density, corresponding to . * The

debye The debye (symbol: D) (; ) is a CGS unit (a non- SI metric unit) of electric dipole momentTwo equal and opposite charges separated by some distance constitute an electric dipole. This dipole possesses an electric dipole moment whose value is g ...

(D) is a unit of electric dipole moment equal to , corresponding to ~. * The buckingham (B) is a unit of electric quadrupole moment equal to .

Electromagnetic radiation

* The jansky (Jy) is a unit of spectral irradiance equal to 10⁻²⁶ W⋅m⁻²⋅Hz⁻¹ (). * The

solar flux unit The solar flux unit (sfu) is a convenient measure of spectral flux density often used in solar radio observations, such as the F10.7 solar activity index: :1 sfu = 104 Jy = 10−22 W⋅m−2⋅Hz−1 = 10−19 erg⋅s−1⋅cm−2⋅Hz� ...

is a unit of spectral irradiance equal to 10⁻²² W⋅m⁻²⋅Hz⁻¹ (). * The nox (nx) is a unit of

equal to 1 millilux (). * The nit (nt) is a unit of luminance equal to one

per metre squared (). * The

lambert Lambert may refer to People *Lambert (name), a given name and surname * Lambert, Bishop of Ostia (c. 1036–1130), became Pope Honorius II *Lambert, Margrave of Tuscany ( fl. 929–931), also count and duke of Lucca *Lambert (pianist), stage-name ...

(L) is a unit of luminance equal to 10⁴/π cd⋅m⁻². * The lumerg is a unit of luminous energy equal to lumen-seconds (100 nlm s). * The talbot (T) is a unit of luminous energy equal to one lumen-second (). * The einstein (E) is a unit of amount of

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are Massless particle, massless ...

s, equal to one mole (1 mol) of photons. * The

rayleigh Rayleigh may refer to: Science *Rayleigh scattering *Rayleigh–Jeans law *Rayleigh waves *Rayleigh (unit), a unit of photon flux named after the 4th Baron Rayleigh *Rayl, rayl or Rayleigh, two units of specific acoustic impedance and characte ...

(R) is a unit of photon flux rate density equal to 10¹⁰ m⁻²⋅s⁻¹ (10⁴ mm⁻²⋅s⁻¹).

Radioactivity

* The

rad RAD