CGS system: centimeter, gram, second
FPS system : foot, pound, second
foot, yard, miles...
MKS system : meter, kg, second.
SI : System Internationale des Unites
This is a complete set of units and used in all countries.
meter, kg, second, ampere for current, degree Kelvin for temperature.
candela is the unit for luminous intensity of light.
mole is the unit for amount of substance or material.
The magnitudes of the basic units are defined in terms of standards,which are supposed to be stable and unchanging.