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IEVref: | 112-02-05 | ID: | |

Language: | en | Status: Standard | |

Term: | metre | ||

Synonym1: | meter, US [Preferred] | ||

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Synonym3: | |||

Symbol: | m | ||

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 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). | ||

Publication date: | 2020-12 | ||

Source: | SI Brochure, 9th edition, 2019, 2.3.1, modified – The definition in the SI Brochure has been revised to comply with the IEV rules. Notes 1 and 2 to entry have been added. | ||

Replaces: | 112-02-05:2010-01 | ||

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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 Δ*ν*_{Cs}."

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).