Meter (m)
Definition: The meter (symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, it is formally defined as the length of the path travelled by light in a vacuum during a time interval of 1/299,792,458 of a second.
History/origin: The meter was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole along the meridian through Paris. Over the centuries the definition was refined multiple times: first tied to a physical platinum-iridium bar, then to the wavelength of light, and finally to the speed of light.
Current use: The meter is the primary unit of length in virtually every country in the world. It is used in science, engineering, construction, and everyday measurement everywhere the metric system has been adopted.
