Every periodic motion is oscillatory, but not vice versa. True or False?

Every periodic motion is oscillatory because it involves the repeated motion of an object around a central point or equilibrium position. 

Here are some examples of periodic motion that are also oscillatory:

1. A pendulum swinging back and forth with a regular period.
2. A spring-mass system vibrating up and down in simple harmonic motion.
3. Waves moving up and down in a body of water or in a vibrating string.

However, not all oscillatory motions are periodic, as they may not have a consistent pattern of repetition over time. 

For example, a swinging pendulum is an example of periodic motion, where the pendulum bob oscillates back and forth with a regular period. On the other hand, a mass attached to a spring that slowly loses energy due to friction is an example of oscillatory motion that is not periodic because its amplitude decreases over time and the motion eventually stops.