Definition:Metric System/Length/Metre

Metre
The metre (US English: meter) is the SI base unit of length.

It was initially invented as $10^{-7}$ the distance from the Earth's equator to the North Pole (at sea level).

Since $1983$, it is defined as the distance travelled by light in vacuum in $\dfrac 1 {299 \ 792 \ 458}$ of a second.

The symbol for the metre is $\mathrm m$.