The fundamental units of length in the metric system (International Systems of Units, SI), equivalent to approximately 39.37 inches. Defined as the distance travelled by light in a vacuum in 1/299,792,458 second. Historically, the meter was defined by the French Academy of Sciences in 1791 as 1/10,000,000 of the quadrant of the Earth’s circumference from the North Pole through Paris to the equator. (en)