180degree

180degree is a term used to denote a half-turn, equal to 180 degrees in angular measurement. It can describe a straight angle, a reversal of orientation, or a rotation of an object by half a circle. The concept appears across mathematics, physics, navigation, and media disciplines.

In geometry and trigonometry, 180 degrees represents a straight angle. When an angle measures 180°, its measure is equivalent to pi radians (180° = π radians). Trigonometric values at this angle include cos(180°) = −1 and sin(180°) = 0. The notion also underpins transformations such as reflections and rotations in two-dimensional space.

In film, photography, and visual media, the 180-degree rule is a storytelling convention that maintains consistent screen direction. An imaginary axis connects characters or objects, and the camera should stay on one side of this axis to preserve spatial relationships. Crossing the axis between shots can create disorientation for the audience. The rule is a guideline rather than an absolute, and violations are sometimes used deliberately for effect.

In navigation, aviation, and robotics, a 180-degree turn signifies a reversal of course or heading. In robotics and computer graphics, a 180-degree rotation is a common operation to reorient components or images. The term also appears in general usage as an adjective (180-degree turn) or as a noun (a 180 degrees rotation).

Variant spellings include 180-degree, 180 degree, and the symbol 180°.