A chord is a line segment whose endpoints are on a circle. A
diameter is a chord that passes through the center of a circle.
Another one of the parts of a circle is a radius, which is a
line segment with one endpoint at the center and one endpoint on
the circle. Congruent circles have congruent radii (the plural
of radius). Concentric circles have the same center. A central
angle has a vertex on the center and endpoints on the circle.
The definition of a circle is the set of all points in the same
plane that are a given distance from a given point. So here we
have a given point, our center, and the circle, which is the
black line. And those are all the points that are a given
distance away from the center. And that given distance is your
radius. If you have a chord or a segment that passes through the
center, that is called a diameter. Now, two commonly confused
terms regarding circles are congruent circles and concentric
circles. Circles whose radii have the same measure are
congruent. Circles who share the