9f7dbe57__units___UK_Metric_Association_SI_base_units_it_measures_and_its_definition
[Unit name] metre [Symbol] m
Length or distance The metre is a unit of distance and is the basis for measuring length, area and volume. The metre was originally derived from one ten millionth of the distance from Earth's pole to the equator but has been refined (1) several times to link it to more stable physical constants. It is now defined in terms of the distance travelled at the speed of light during a very precisely defined fraction of a second. The length of the path travelled by light in a vacuum during a time interval of 1/299 792 458 of a second.
Base units | UK Metric Association
What it measures and its definition