That curved piece of the circle and the interior space is called a sector, like a slice of pizza. If you take less than the full length around a circle, bounded by two radii, you have an arc. You can also measure the circumference, or distance around, a circle. This angle measure can be in radians or degrees, and we can easily convert between each with the formula π r a d i a n s = 180 °. An arc measure is an angle the arc makes at the center of a circle, whereas the arc length is the span along the arc. An arc is a segment of a circle around the circumference.
