**There are four system of units:**

（i) F.P.S.(Foot-Pound-Second) system.

（ii) C.GS. (Centimetre – Gramme – Second) system.

（iii) M.K.S.(Metre-Kilogramme-Second) system.

（iv) S.I. (System International or International System).

（i) ** F.P.S. System: **In this system, the units of length, mass, and time are foot, pound, and second

respectively.

（ii) ** C.G.S.System:** In this system, the units of length, mass, and time are centimetre, gram and

second respectively.

（iii) ** M.K.S.System: In this system, **the units of length, mass, and time are metre, kilogram and

second respectively.

（iv) ** S.I. units or International system of units:** S.I. is based on seven basic units and two

supplementary units.