The phenomenon where two waves combine to form a larger wave is called "constructive interference." This occurs when the crests (high points) of one wave align with the crests of another, resulting in a wave with greater amplitude. Conversely, if the crests of one wave align with the troughs (low points) of another, it leads to "destructive interference," which diminishes the overall wave. Constructive and destructive interference are fundamental concepts in wave mechanics, affecting various fields, including acoustics, optics, and even electromagnetic waves.