Derived units are units which may be expressed in terms of base units by means of mathematical symbols of multiplication and division.

Certain derived units have been given special names and symbols, and these special names and symbols may themselves be used in combination with the SI and other derived units to express the units of other quantities.

Examples of SI derived units expressed in terms of base units
Derived Quantity	SI derived unit
	Name	Symbol
area	square metre	m2
volume	cubic metre	m3
speed, velocity	metre per second	m/s
acceleration	metre per second squared	m/s2
wavenumber	1 per metre	m-1
density, mass density	kilogram per cubic metre	kg/m3
specific volume	cubic metre per kilogram	m3/kg
current density	ampere per square metre	A/m2
magnetic field strength	ampere per metre	A/m
concentration (of amount of substance)	mole per cubic metre	mol/m3
luminance	candela per square metre	cd/m2
refractive index	(the number) one	1(a)
(a) The symbol '1' is generally omitted in combination with a numerical value.