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 an up and down movement of water. When we talk about waves, we use special words to name their parts. The highest point of a wave is called the crest. The lowest point is called the trough. Wave height is the vertical distance between the crest and trough. Wavelength is the horizontal distance between waves in a series. Wavelength can be measured between two wave crests. It can be measured between two wave troughs.