The SI System of Units

Abstract

The present advanced state of the pure and applied sciences could not have been achieved without experimentation and without measurements made with the utmost accuracy possible with existing resources. By measurement we mean comparison with something of the same physical nature which is regarded as a standard. Hence, in order to state the magnitude of any physical entity we make use of two concepts, a numeric and a unit. A numeric is a number and it may be integral or fractional, positive or negative. A unit is a physical entity of such magnitude that it has a numeric of unity. Thus if we say that an electric current is equal to 10 amperes, 10 is the numeric and ampere is the name given to a current of such magnitude that it is equal to the accepted unit of current.