||This article relies largely or entirely upon a single source. (November 2010)
The millimetre (American spelling: millimeter; SI unit symbol mm) is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length.
It is equal to 1,000 micrometres and 1,000,000 nanometres. There are 25.4 mm in one inch.
Unicode symbols 
For the purposes of compatibility with Chinese, Japanese and Korean (CJK) characters, Unicode has symbols for:
- millimetre (㎜) - code U+339C
- square millimetre (㎟) - code U+339F
- cubic millimetre (㎣) - code U+33A3
They are useful for East Asian fixed-width CJK typography, because they are equal in proportion to one Chinese character.
See also