SI base unit

The SI base units are:

Physical quantity	Symbol	Name of SI base unit	Symbol for SI unit
length	l	metre	m
mass	m	kilogram	kg
time	t	second	s
electric current	I	ampere	A
thermodynamic temperature	T	kelvin	K
amount of substance	n	mole	mol
luminous intensity	Iv	candela	cd

All other physical units can be derived from these seven SI base units.

The SI prefixes are applied to abbreviate long numbers.

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To do: merge Standards and Units with this. Incorporate operational definitions of units.