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. Hence a centimetre can be written as 10×10 m (engineering notation) or (scientific E notation) — meaning or respectively. The centimetre is the base unit of length in the now deprecated 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.
The centimeter is the distance light travels through a vacuum in second.
1 cubic centimetre is equal to 1 millilitre, under the current SI system of units.
They are useful only with East Asian fixed-width CJK fonts, because they are equal in size to one Chinese character.