Mathematics deals with two distinct branches of studies, namely time and space. Time stands for Cardinal or Ordinal countings and related operatios. Space stands for all sorts of Geometrical operations and related practices. Smallest figure in the field of pace is a point. Series of collinear points give birth to rays. In the similar way lines, line segments and other figures come in existence.
Similarly unit of number is 1. Entire number system that we follow in Mathematics is also called a decimal system because of the involvement of ten (Decim) digits in the formation all other numbers including decimals, fractions and rationals. In all cases the word decimal will indicate the use of ten digits in forming the number.