The ability of two or more waves to overlap and form a new wave is known as interference. It occurs when two waves meet while traveling through the same medium.
Wave interference causes a new wave to form with a new shape. Constructive interference occurs when the two interfering waves have the same displacement in the same direction. Constructive interference forms a new wave with a larger displacement than the two original interfering waves. Destructive interference occurs when two waves have displacements in opposite directions. The result of destructive interference is two waves that move in opposite directions from the original two interfering waves.