A motion is periodic if it repeats itself at regular intervals. We call the repeated movement a full swing.

The time it takes for an oscillation to complete a full oscillation is called the oscillation period (we denote it by the letter $T$).

The number of complete oscillations per unit time during oscillation is called the oscillation frequency (here we denote it by the letter $f$). From the oscillation period $T$, the oscillation frequency is manifested in the form $f$

The unit of oscillation frequency $1Hz$ is one complete oscillation per second, $1Hz=1s^{–1}$.

The distance of the oscillating body from the equilibrium position is called the deviation of the body. The maximum deviation, or the greatest distance from the equilibrium position, is called the oscillation amplitude.