Diameter

The diameter of a circle or sphere is the longest straight line that passes through its center, touching both sides. It essentially measures how wide the object is at its widest point. For a circle, if you draw a line from one edge to the opposite edge through the middle, that's the diameter. It’s twice the length of the radius, which is the distance from the center to the edge. The diameter helps describe the size of round objects accurately and is used in many calculations involving circles and spheres.