Millimeter

The millimetre (international spelling as used by the International Bureau of Weights and Measures; SI unit symbol mm) or millimeter (American spelling) is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length. Therefore, there are one thousand millimetres in a metre. There are ten millimetres in a centimetre. The millimetre (international spelling as used by the International Bureau of Weights and Measures; SI unit symbol mm) or millimeter (American spelling) is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length. Therefore, there are one thousand millimetres in a metre. There are ten millimetres in a centimetre. One millimetre is equal to 1000 micrometres or 1000000 nanometres.Since an inch is officially defined as exactly 25.4 millimetres, a millimetre is therfore equal to exactly ​5⁄127 (≈ 0.03937) of an inch. Since 1983, the metre has been defined as 'the length of the path travelled by light in vacuum during a time interval of 1/299792458 of a second'. A millimetre, 1/1000 of a metre, is therefore the distance travelled by light in 1/299792458000 of a second. A common shortening of millimetre in spoken English is 'mil'. This can cause confusion since in the United States, 'mil' traditionally means a thousandth of an inch. For the purposes of compatibility with Chinese, Japanese and Korean (CJK) characters, Unicode has symbols for: