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A degree, denoted by a small circle superscript (°), is a unit of angular measure constituting one 360th part of a complete revolution (or circle).

The reason for there being 360° in a circle isn't completely understood. It may have something to do with being close to the number of days in a year (between 365 and 366). Mathematically, however, it appears to be an arbitrarily chosen value.

Alternative units of angular measure include:

• The grad, one 400th part of a circle — which makes the arithmetic easier to do without a computational aid.