In waves, the crest appears as the highest point, while the trough is the lowest, forming a dip or valley in the wave's motion. The crest, also called the peak, forms the maximum height of every wave, including water waves, radio waves and electrical waves. The distance and height between the trough and crest varies depending on the type of wave and local conditions, such as wind speed and direction.
The crest rises above the level of still water, which in turn determines wave height. Similarly, scientists measure the distance of the trough as the lowest point in comparison to the standing water level or line of equilibrium. Waves form from many sources, which influences height and wave length. Water waves arise from the movement of boats and currents, but occur primarily from the force of winds. Wind speed and direction, called fetch, makes water rise. The height of the waves depends on these factors, while wave length and distance depend on the duration, strength and frequency of wind gusts. Wave length refers to the greatest horizontal distance between two waves, which measures from the crests or troughs. Wave height and length determine wave frequency, which identifies the amount of time elapsing between each wave passing over a set, fixed point.