Rotational motion: Purely rotational motion occurs if every particle in the body moves in a circle about a single line. This line is called the axis of rotation Linear motion: Moving in a straight line. Periodic motion: Motion repeated in equal intervals of time.
A stone suspended with a non-stretchable thread makes a simple pendulum. When the pendulum is at rest, it is at position B. This is called the rest position or its mean position. When it swings, it moves from B to A, back to B, from B to C and back to B. This completes one full swing of the pendulum. Each swing is called one oscillation.