1. a portion of the circumference of a circle
arc measure
2. an arc which measures exactly 180°
semicircle
3. an arc which measures less than 180°
diameter
4.
the degree measurement of an arc (in reference to its central
angle)
minor arc
5. the distance around a circle
circumference
6. the distance through the center between points on a circle
arc length
7. the distance from the center to any point on a circle
radius