A central angle is an angle whose vertex is located at the center of a circle. It is formed by two radii (plural of radius) that extend from the center to the circumference. The measure of a central angle is equal to the measure of the arc it intercepts on the circle. Central angles are important in geometry and are used to calculate various properties of circles, such as the length of an arc and the area of a sector. They help in understanding the relationship between angles and arcs in circular shapes, which is essential in fields like trigonometry and engineering.