Amplitude, in physics, the maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. It is equal to one-half the length of the vibration path.

The Amplitude is the height from the center line to the peak (or to the trough). Or we can measure the height from highest to lowest points and divide that by 2.

Amplitude is the size of the vibration, and this determines how loud the sound is. We have already seen that larger vibrations make a louder sound. Amplitude is important when balancing and controlling the loudness of sounds, such as with the volume control on your CD player.

The amplitude of a wave is its maximum disturbance from its undisturbed position.

Amplitude (of sound) is the objective measurement of the degree of change (positive or negative) in atmospheric pressure, or the compression and rarefaction of air molecules caused by sound waves.