**Definition: **(1) The meter is the basic unit of length in the SI system of units. The meter is defined to be the distance light travels through a vacuum in exactly 1/299792458 seconds. 1 m is about 39.37 inches. Meters are abbreviated using a lower case "m" in measurements. (2) A meter is any device which measures and records the quantity of a substance. (3) A meter is any device which measures and may record an electrical or magnetic quantity, such as voltage or current.

**Also Known As: **m

**Alternate Spellings: **metre