Crest: The crest is the point on a wave in which the displacement is the highest.
Trough: A trough is the point on a wave in which the displacement is the lowest.
Amplitude: The amplitude is the maximum displacement or distance moved by a point on a wave.
Transverse Displacement: The transverse displacement is any point above or below the equilibrium.
Compression: Compression in a wave is the high pressure region in a wavelength.
Rarefaction: Rarefaction is the low pressure region in a wavelength.