Every oscillatory motion is necessarily periodic but every periodic motion need not be oscillatory. Justify.

Explanation

Oscillatory motion means to-and-fro motion or back and forth motion. For example, motion of a pendulum. Periodic motion is a motion that repeats itself after a fixed interval of time. Oscillatory motion always repeats after certain interval of time. Thus they are periodic but all periodic motions are not oscillatory. Motion of planets around the Sun is periodic because it repeats itself after a fixed interval of time but cannot perform to and fro motion so it is not oscillatory motion.