circle
the set of all points in a plane that are the same distance from some point called the center
radius
a segment whose endpoints are the center of the circle and any point on the circle
chord
a segment whose endpoints are any two points on a circle
diameter
a chord that passes through the center of a circle
central angle
an angle with its vertex at the center of a circle
degree
the most commonly used unit for measuring angles
acute angle
an angle with measure less than 90 degrees
right angle
an angle with measure equal to 90 degrees
obtuse angle
an angle with measure greater than 90 degrees, but less than 180 degrees
straight angle
an angle with measure equal to 180 degrees