Dimensionless numbers, abbreviated as DN, are nondimensional quantity of dimension one and can not be measured on a scale of physical units. All quantities of dimension one are said to have the SI coherent derived unit "one" with the symbol "1". It is a pure number, thus always having a dimension of 1. The number does not change even if the number system you are working in does. Dimensionless numbers or quantities are used in many disiplines such as chemistry, economics, engineering, mathematics, and physics.