How many degrees are in a right angle?

A right angle is defined as the angle formed when two lines are perpendicular to each other. In standard geometric terms, a right angle measures exactly 90 degrees. This universally accepted definition is foundational in various branches of mathematics, particularly in geometry, where right angles play a crucial role in establishing the properties of shapes, particularly rectangles and squares.

The other options represent different types of angles: 45 degrees corresponds to an acute angle, 180 degrees denotes a straight angle, which forms a straight line, and 360 degrees signifies a full rotation, returning to the starting position. Therefore, 90 degrees is the precise measurement for a right angle, confirming why it is the correct choice in this question.