micrometre

A micrometre (American spelling: micrometer; symbol µm) is an SI unit of length equal to one millionth of a metre, or equivalently, one thousandth of a millimetre. It is also commonly known as a micron. It can be written in scientific notation as 1×10−6 m, meaning .The symbol µm's character µ (Unicode character U+00B5; HTML µ) is "micro-", which should look identical to the Greek letter mu (μ) (the two may or may not look the same, depending on the  font). The symbol "um" is sometimes used, when the µ and μ are not available, for example in  ASCII, or when using a typewriter.
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n. micrometer, instrument for microscopic or tiny measurements

<unit> (Or "micron") One millionth of a metre. The symbol is a Greek letter mu followed by "m".
Features on modern integrated circuits are typically measured in microns. The smallest features in 1999 are around 0.1 microns across.
(1999-09-28)