Question

Why is the motion of a simple pendulum said to be oskillatory not a vibratory motion​

Answer 1

Vibration is the periodic motion and the restoring force is the Force due to elastic property of body. Rigid body can not vibrate. Anything has mass and elasticity can vibrate.

Oscillation is also Periodic motion and restoring force is due to weight of the body. even rigid body can oscillate.

IN case of pendulum restoring force is weight of the body itself so the motion is oscillatory motion.