Mach
Symbol: Ma or M
Mach is the speed of an object moving through air, or any fluid substance, divided by the speed of sound as it is in that substance.
The Mach number is named after the Czech/Austrian physicist Ernst Mach. The speed of sound differs by temperature and so this unit depends on the enviromental conditions. At a temperature of 20°C, Mach 1 equates 343m/s and 1m/s equals Mach 0.00291.