What is the portion of the circumference of a circle called?

The correct term for the portion of the circumference of a circle is an arc. An arc is defined as a segment of the circumference, representing a continuous part of the path along the circle's edge. It is specified by two endpoints on the circle and can vary in length, depending on the angle that subtends it at the center of the circle.

Understanding what distinguishes an arc from other terms is helpful. A chord, for instance, connects two points on the circle but does not follow the curvature of the circle. The diameter is a specific type of chord that passes through the center of the circle and is the longest possible distance across it. The radius refers to the distance from the center of the circle to any point on the circumference. Thus, while all these terms relate to parts of a circle, the arc specifically describes that curved segment of the circumference.