Arcs

Arcs are continuous portions of curves between two endpoints. In geometry, an arc denotes a portion of a circle's circumference, defined by its endpoints and which part of the circle is used. Minor arcs are shorter than a semicircle; major arcs are longer. A semicircular arc spans 180 degrees. The length s of an arc with radius r and central angle θ (in radians) is s = rθ; in degrees, s = πrθ/180. An arc can be named by its endpoints, often with an additional point to distinguish which arc is meant (for example, arc AB or arc ACB). For general smooth curves, the term arc refers to any continuous segment measured by arc length.

In narrative theory, a plot arc describes the progression of a story or a character across a work, typically involving setup, rising action, climax, and resolution.

In electrical engineering, an electrical arc is a discharge of electricity through a gas between two electrodes. This plasma discharge can produce intense heat and light and is central to processes such as arc welding and arc furnaces, but it also poses safety hazards such as burns and arc flash.

Outside mathematics and engineering, the term arc is used to describe curved architectural or typographic elements derived from circular geometry.