A curve, or bend, refers to a smooth, continuous change in direction of a line or surface. Curves can be found in various contexts, such as in geometry, where they represent shapes like circles and ellipses, or in nature, like the arcs of rivers and the contours of hills. In mathematics, curves are often described using equations that define their shape and properties. For example, the parabola is a type of curve that can be represented by a quadratic equation. Curves play a significant role in fields like physics, engineering, and art, influencing design and structure.