Metre: Learn how the metre

Learn how the metre, the SI unit of length, is defined by the speed of light in vacuum and the caesium frequency. Find out the historical evolution and practical realization of the metre. Meter and metre are two spellings that often cause confusion. For the unit of measurement, equaling approximately 1.094 yards, meter is the American spelling, and metre is preferred in British English. The metre (m), or meter in US spelling - How long would it take to walk around planet Earth? Learn how to spell and use meter and metre, two forms of the same word that refer to a unit of length in the metric system. Meter is preferred in American English, while metre is used in British English and other varieties.