A single rise or depression in a wave is called the ?

The single rise or depression of a wave are known as crest and trough. In case of transverse waves, we can think of wave motion as consisting of a series of ups and downs or hills and valleys. The highest point in this motion or the rise is known as the crest, whereas the lowest point of the depression is called the trough. One can see this type of motion by using a rope and vibrating its end in an up and down motion, we will be able to see the waves traveling from one end to the other. 

There are some other terms associated with these rise and depressions (or crests and troughs). The wavelength is the distance between two consecutive troughs or crests. Similarly, the wave amplitude is defined is as the distance of crest or trough from the centerline (or the central position or position of rest).

Hope this helps.