Centimetre

A centimetre (American spelling: centimeter, symbol cm) is a unit of length in the metric system, equal to one hundredth of a metre, which is the SI base unit of length. Centi is the SI prefix for a factor of 10−2. Hence a centimetre can be written as 1×10−2 m, 10×10−3 m (engineering notation) or 1E−2 m (scientific E notation) — meaning 10 mm or 1 m/100 respectively. The centimetre is the base unit of length in the now deprecated centimetre-gram-second (CGS) system of units.

Though for many physical quantities, SI prefixes for factors of 103—like milli- and kilo-—are often preferred by technicians, the centimetre remains a practical unit of length for many everyday measurements. A centimetre is approximately the width of the fingernail of an adult person (between 3/8 in and 7/16 inch on an English inch ruler).