Here's why:

* Repetitive Motion: A pendulum swings back and forth repeatedly, moving through the same path.

* Equilibrium Position: It has a central equilibrium position where it would rest if undisturbed.

* Restoring Force: When displaced from equilibrium, gravity acts as a restoring force, pulling it back towards the center.

* Periodicity: The time it takes for the pendulum to complete one full swing (back and forth) is relatively constant, known as its period.

Therefore, the cyclical and repetitive motion of a pendulum, driven by a restoring force, makes it a clear example of oscillatory motion.