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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 ( Unicode character U+00B5; HTML µ) is the " micro sign"; it is derived from the Greek letter mu (μ). The symbol "um" is sometimes used, when the µ 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 astronomyAstronomy which etymologically means " law of the stars," (from Greek: + nomos) is a science involving the observation and explanation of events occurring outside Earth and its atmosphere. It studies the origins, evolution, physical and chemical propertie and the semiconductorA semiconductor is a material that is an insulator at very low temperature, but which has a sizable electrical conductivity at room temperature. The distinction between a semiconductor and an insulator is not very well-defined, but roughly, a semiconducto business) use the old name micron and/or the solitary symbol µ for the same thing, even though it is officially discouraged.

nanometreA nanometre ( American spelling: nanometer is 10−9 metres—or one billionth of a metre. Its symbol is nm . It is an SI measure of length, commonly used in measuring the wavelengths of visible light, ultraviolet radiation and gamma rays; amongst other << micrometre << millimetre

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SI derived units of length







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