Degrees:

One of the techniques of specifying fractions of an ac cycle is to divide it into 360 equal increments known as degrees, represented by ° or deg (though it's okay to write out the entire word). The 0° value is assigned to the point in the cycle where the magnitude is zero and positive-going. The similar point on the next cycle is given the value 360°. Halfway via the cycle is 180°; a quarter cycle is 90°; an eighth cycle is 45°. This is demonstrated in figure as shown below.

Figure: A wave cycle can be divided into 360 degrees.