Radiuses are one of the most important geometric shapes used in various fields such as mathematics, engineering, and architecture. A radius is a straight line from the center of a circle to any point on its circumference. In addition to radiuses, there are several synonyms that refer to the same thing, including radii, the plural form of radius, and radii of a circle or spheres. Other synonyms for radiuses include spokes, wings, arms, and rays. No matter which term you use, they all refer to the distance from the center of a circle or sphere to its edge or circumference.