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MicrometreA micrometre (American spelling: micrometer, symbol m) 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 (Unicode character U+00B5; HTML µ) is the "micro sign"; it is derived from 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 and μ are not available, e.g. when using a typewriter. 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 for the same thing, even though it is officially discouraged. They were official from 1879-1967. In many engineering and manufacturing fields, micrometer usually refers to the measuring instrument, thus micron is still prefered when talking about the unit to avoid confusion. nanometre << micrometre << millimetre See also
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