In physics, any regularly recurring event, such as surf coming in toward a beach, that can be thought of as a disturbance moving through a medium. Waves are characterized by wavelength, frequency, and the speed at which they move. Waves are found in many forms.
Note: The motion of a wave and the motion of the medium on which the wave moves are not the same: ocean waves, for example, move toward the beach, but the water itself merely moves up and down. Sound waves are spread by alternating compression and expansion of air.