An "arc" is a segment of a curve, often described as a part of a circle. It is defined by two endpoints and the continuous curve that connects them. In geometry, arcs are used to measure angles and distances, and they can vary in size depending on the radius of the circle from which they are derived. In storytelling, an "arc" refers to the development and progression of a character or plot over time. A character arc illustrates how a character changes, grows, or learns throughout the narrative, while a plot arc outlines the main events and conflicts that drive the story forward. Both types of arcs are essential for creating engaging and cohesive narratives in literature and film.