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.
A wave is defined as a burst of emotions, a swell along the surface caused by wind, a sudden occurrence of something, or a back and forth motion with your hand. When you suddenly feel really sad, this is an example of a wave of sadness. The water movement that you use to go surfing in is an example of a wave.