noun
number of revolutions; rotational speed
Used for engine RPM, motor speed, or any rotating object's revolution count. Often appears in technical contexts.
エンジンの回転数が上がると、車は速くなる。
When the engine's RPM increases, the car goes faster.
このモーターの最高回転数は毎分
The maximum rotational speed of this motor is 3000 revolutions per minute.