motion that recurs over and over and the period of time required for each recurrence remains the same
双语例句
The harmonic oscillator is an exceptionally important example of periodic motion. 谐振子在周期运动中是特别重要的。
The apparent motion is sinusoidal with a wavelength proportional to the distance between the orbits of the satellite and the particle. 这个规律的周期运动,其波长会与粒子和卫星轨道之间的距离成正比。