A

David

Darling

SI (Systeme Internationale) system of units

The SI (Systeme Internationale) system is a coherent and rational system of units, derived from the MKS system, which is used worldwide for scientific purposes. The SI system has seven base units and two dimensionsless (formerly known as supplementary) units – the radian and the steradian. All other units are derived from these basic nine. There are 18 derived units with special names.