SI units

In Europe and the UK, the units for measuring different properties
are known as SI units. SI stands for Système Internationale.
All units are derived from seven base units.

Base quantity	Base unit	Symbol
Time	Second	s
Electrical current	Ampere	A
Length	Metre	m
Mass	Kilogram	kg
Temperature	Kelvin	K
Luminous intensity	Candela	cd
Amount of substance	Mole	mol

SI-derived units:

Derived quantity	Name	Symbol
Frequency	Hertz	Hz
Force	Newton	N
Energy, work, quantity of heat	Joule	J
Electric charge, quantity of electricity	Coulomb	C
Power	Watt	W
Potential difference, electromotive force	Volt	V or U
Capacitance	Farad	F
Electrical resistance	Ohm	Ω
Magnetic flux	Weber	Wb
Magnetic flux density	Tesla	T
Inductance	Henry	H
Luminous flux	Lumen	lm
Area	Square metre	m²
Volume	Cubic metre	m³
Velocity, speed	Metre per second	m/s
Mass density	Kilogram per cubic metre	kg/m³
Luminance	Candela per square metre	cd/m²

SI unit prefixes:

Name	Multiplier	Prefix	Power of 10
Tera	1000 000 000 000	T	1×1012
Giga	1000 000 000	G	1×109
Mega	1000 000	M	1×106
Kilo	1000	k	1×103
Milli	0.001	m	1×10-3
Micro	0.000 001	µ	1×10-6
Nano	0.000 000 001	η	1×10-9
Pico	0.000 000 000 001	ρ	1×10-12

[Electrical Installation Calculations Basic, 8th Edition - p5,6]