The diameter of a circle is defined as the distance across the circle through which point?

• A. Distance around the circle
• B. Radius length
• C. Chord length
• D. Distance across the circle through the center

Answer: (D)

The diameter is the distance across the circle that passes through the center. It is the longest chord of a circle, with endpoints on the circle and the line going straight through the middle. This makes it distinct from the circumference, which is the distance around the circle, and from the radius, which is the distance from the center to the edge. A chord is any line segment joining two points on the circle; the diameter is a special chord that passes through the center, so its length is twice the radius.