Howdy! can be replied to with just a nod and a smile. It simply means Hi! in Texan - not How are you doing?. Or you might reply, Hey Y'all Doon? if you want to engage in proper Texan interactions. Replying in proper English, well pronounced, with each syllable clearly spoken, is HIGHLY discouraged.
The crest of a wave is the point of maximum positive displacement, or upward movement, away from equilibrium, or an undisturbed state. The opposite of crest is trough, which is the point of the greatest negative, downward displacement.
Crests and troughs occur in transverse waves. A transverse wave is a wave where particles of the medium move in a direction perpendicular to the direction the energy is moving. There are three main components of a transverse wave: crest, trough and equilibrium. Amplitude of a wave is the distance the energy travels from equilibrium to crest/trough.