+**Mach** is a dimensionless quantity representing the ratio of an object's speed to the [speed of sound](/wiki/speed_of_sound) in the surrounding medium. Named after physicist [Ernst Mach](/wiki/ernst_mach), it is a critical measure in [aerodynamics](/wiki/aerodynamics) for characterizing flow regimes, from subsonic to hypersonic velocities.
+## See also
+- [Supersonic](/wiki/supersonic)
+- [Shock Wave](/wiki/shock_wave)
+- [Fluid Dynamics](/wiki/fluid_dynamics)