International System (SI) Units Definition

Physical Quantity	Name of Unit	Unit Symbol	Definition
Length	meter	m	Distance traveled by light in vacuo during 1 ⁄299, 792, 458 of a second.
Mass	kilogram	kg	Mass of the international prototype which is in the custody of the Bureau International des Poids et Mesures (BIPM) at Sèvres, near Paris.
Time	second	s	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 cesium-133 atom.
Electric Current	ampere	A	The constant current which, if maintained in two parallel rectilinear conductors of infinite length, of negligible circular cross section, and placed at a distance of one meter apart in a vacuum, would produce between these conductors a force equal to 2 × 10−7 N/m length
Thermodynamic Temperature	degree Kelvin	K	The fraction 1⁄273.16 of the thermodynamic temperature of the triple point of water.
Amount of Substance	mole	mol	The amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12.
Luminous Intensity	candela	cd	Luminous intensity, in the perpendicular direction, of a surface of 1⁄600,000 square meter of a black body at the temperature of freezing platinum under a pressure of 101,325 newtons per square meter.
Force	newton	N = Kg.m/s2	That force which, when applied to a body having a mass of one kilogram, gives it an acceleration of one meter per second squared.
Work, Energy, Quantity of Heat	joule	J = N.m	The work done when the point of application of a force of one newton is displaced through a distance of one meter in the direction of the force.
Electric Charge	coloumb	C = A.s	The quantity of electricity transported in one second by a current of one ampere.
Electric Potential	volt	V = W/A	The difference of potential between two points of a conducting wire carrying a constant current of one ampere, when the power dissipated between these points is equal to one watt.
Electric Capacitance	farad	F = C/V	The capacitance of a capacitor between the plates of which there appears a difference of potential of one volt when it is charged by a quantity of electricity equal to one coulomb.
Electric Resistance	ohm	Ω = V/A	The resistance between two points of a conductor when a constant difference of potential of one volt, applied between these two points, produces in this conductor a current of one ampere, this conductor not being the source of any electromotive force.
Magnetic Flux	webber	Wb = V.s	The flux which, linking a circuit of one turn produces in it an electromotive force of one volt as it is reduced to zero at a uniform rate in one second.
Inductance	henry	H = V.s/A	The inductance of a closed circuit in which an electromotive force of one volt is produced when the electric current in the circuit varies uniformly at the rate of one ampere per second.
Luminous Flux	lumen	lm = cd.sr	The flux emitted within a unit solid angle of one steradian by a point source having a uniform intensity of one candela.
Illumination	lux	lx = lm/m2	An illumination of one lumen per square meter.

Encyclopaedia of Scientific Units, Weights and Measures: Their SI Equivalences and Origins