1) A circle is set of all points at the same distance from its center. It is named by its center.
2) A chord of a circle is a line segment whose endpoints lie on the circle.
3) A tangent to a circle is a line which touches the circle at only one point.
4) Point of tangency is the point of contact of the circle and the tangent line.
5) Secant is the line that intersects a circle at two points.
6) An arc is the broken part of the circle. The three types of which are: minor arc, major arc, and semicirle.
7) A central angle is an angle whose vertex is the center of the circle and whose sides are the radii of the circle.
8) The degree measure of a minor arc is less than 180 degrees.
9) The degree measure of a major arc is 360° minus the degree measure of the minor arc.
10) Circles are concentric if they lie in the same plane, they have the same center, and they have radii of different lengths.
11) If the length of the radii of two circle are equal, then the two circles are congruent.
12) Any two congruent chords are equal from the center.
13) A line from the center perpendicular to a chord, bisects the chord.
14) The perpendicular bisector of a chord of a circle passes through the center of the circle.
15) If a radius bisects a chord and its arc then the radius is perpendicular to the chord.
