Oscillatory or vibratory motion is that motion in which a body moves to and fro or back and forth repeatedly about a fixed point in a definite interval of time. In such a motion, the body is confined with in well-defined limits on either side of mean position.

Oscillatory motion is also called as harmonic motion.

Example :

(i) The motion of the pendulum of a wall clock.

(ii) The motion of a load attached to a spring, when it is pulled and then released.

(iii) The motion of liquid contained in U- tube when it is compressed once in one limb and left to itself.

(iv) A loaded piece of wood floating over the surface of a liquid when pressed down and then released executes oscillatory motion.