When two waves interact with their crests and troughs in alignment is called?

When two waves interact with their crests and troughs in alignment is called constructive interference. If two waves of the same wavelength occupy the same space in such a way that their crests and troughs align, the wave they produce will have an amplitude greater than that possessed by either wave initially. This is known as constructive interference. The more closely the waves are in phase-that is, perfectly aligned-the more constructive the interference.