Definition:Fundamental Unit (Physics)

Definition
A set of fundamental units is a set of units of measurement for physical quantities from which every other unit can be generated.

They are the units of the fundamental dimensions of physics.

Conventions
There are various conventions, as follows:
 * SI units (Système International), which evolved from the MKS system;
 * MKS, that is, Meter-Kilogram-Second;
 * CGS, that is, Centimeter-Gram-Second;
 * Imperial or FPS: that is, Foot-Pound-Second.

There are other more specialized ones.