물체의 속도와 그 매질 속에서의 음속과의 비를 나타내는 수치.
A dimensionless quantity representing the ratio of the speed of an object to the speed of sound in the surrounding medium.
예문:
"The experimental aircraft successfully reached Mach 3 over the desert."
"At high altitudes, the Mach number is a more critical measurement than ground speed."