The **meter** (symbol **m**) is the metric and SI base unit of distance. Originally, the meter was designed to be one ten-millionth of a quadrant. For a long time, the meter was precisely defined as the length of an actual object, a bar kept at the International Bureau of Weights and Measures in Paris. In recent years, however, the SI base units (with one exception) have been redefined in abstract terms so they can be reproduced to any desired level of accuracy in a well-equipped laboratory. The 17th General Conference on Weights and Measures in 1983 defined the meter as that distance that makes the speed of light in a vacuum equal to exactly 299 792 458 meters per second. The speed of light in a vacuum, *c*, is one of the fundamental constants of nature. Since *c* defines the meter now, experiments made to measure the speed of light are now interpreted as measurements of the meter instead. The meter is equal to approximately 1.093 613 3 yards, 3.280 840 feet, or 39.370 079 inches. Its name comes from the Latin *metrum* and the Greek *metron*, both meaning "measure." The unit is spelled *meter* in the U.S. and *metre* in Britain; there are many other spellings in various languages.