**Speed**

From Wikipedia, the free encyclopedia.

*For alternative meanings of***Speed**, see Speed (disambiguation).

**Speed**is the rate of motion expressed as distance moved per unit of time. Speed is a scalar quantity; the equivalent vector quantity is known as velocity.

Units of speed include:

- meter per second, (symbol m/s), the SI derived unit
- kilometer per hour, (symbol km/h)
- mile per hour, (symbol mph)
- knot (nautical miles per hour)
- Mach, where Mach 1 is the speed of sound; Mach
*n*is*n*times as fast.