wiki says: 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 current si base unit of length. Centi is the si prefix for a factor of 10−2.[1] hence a centimetre can be written as 10 × 10−3 m (engineering notation) or 1e−2 m (scientific e notation) — meaning 10 × 101 mm or 1 m/100 respectively,centimetre-gram-second 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.