Micrometre
A micrometre (American spelling: micrometer), symbol µm is an SI unit of length. It is defined as one millionth of a metre (1 × 10−6 m), equivalent to one thousandth of a millimetre. The symbol µ is the "micro sign"; it is derived from the Greek letter mu (μ). The micrometre is a common unit of measurement for wavelengths of infrared radiation.Some people (especially in astronomy and the semiconductor business) use the old name micron and/or the solitary symbol µ, for the same thing, even though it is officially discouraged.
A micrometer is the name of a tool that measures the thickness of objects. In American English, the spelling of the tool and the unit are identical.
nanometre << micrometre << millimetre
See also
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