The diameter of a circle is a line segment which passes through its center and intersects its perimeter (or circumference) at two opposite points. The length of the circle's diameter is twice its radius (distance from center to any point on the circle). Often, one simply speaks of "the diameter" while referring to the length of the diameter.
- Wile, Dr. Jay L. Exploring Creation With General Science. Anderson: Apologia Educational Ministries, Inc. 2000