n.
Basic unit of length in the metric system and the International System of Units .
In 1983 the General Conference on Weights and Measures decided that the accepted value for the speed of light would be exactly 299,792,458 metres per second, so the metre is now defined as the distance traveled by light in a vacuum in 1/299,792,458 second. One metre is equal to about 39.37 in. in the U.S. Customary System.