Physical quantities and units

SI units

SI units defines 7 base quantities and units.
QUANTITIES                                UNITS
Time-> t                                second-> s
Length-> l                              metre-> m
Mass-> m                              kilogram-> kg
Temperature-> T                    kelvin-> K
Electric current-> I                 ampere-> A
Amount of substance-> n        mole-> mol
Luminous intensity                   candela-> cd

We use prefixes for SI units such as tera, giga, mega, kilo, deci etc. They all are representations of the standard forms.