Micrometre

A micrometre (or micrometer) is 1×10−6 of a metre (SI Standard prefix "micro" = 10−6); that is, one-millionth of a metre (or one-thousandth of a millimetre, 0.001 mm, or about 0.000039 inches). Its unit symbol in the International System of Units (SI) is µm. The latter may be rendered as um if Greek fonts are not available or not admissible.