UNITS

Units of speed include:

Meters per second (symbol m s⁻¹ or m/s), the SI derived unit;

Kilometers per hour (symbol km/h);

Miles per hour (symbol mph);

Knots (nautical miles per hour, symbol kn or kt);

Feet per second (symbol fps or ft/s);

Mach number, speed divided by the speed of sound;

The speed of light in vacuum (symbol c) is one of the 

natural units: c = 299,792,458 m/s.