| Definition: | SI unit of length, equal to the length of the path travelled by light in vacuum in a duration of 1/299 792 458 s
Note 1 to entry: The definition in the SI Brochure is: "The metre, symbol m, is the SI unit of length. It is defined by taking the fixed numerical value of the speed of light in vacuum c to be 299 792 458 when expressed in the unit m s−1, where the second is defined in terms of the caesium frequency ΔνCs."
Note 2 to entry: The metre is one of the seven SI base units: second (s), metre (m), kilogram (kg), ampere (A), kelvin (K), mole (mol) and candela (cd).
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