What is the distance across a circle through its center called?

The term for the distance across a circle that passes through its center is known as the diameter. The diameter is defined as the longest distance across the circle and essentially consists of two radii, extending from the center of the circle to its edge on either side. This measurement gives a full span of the circle at its widest point.

The concept of the diameter is crucial in various geometric calculations, including finding the area and circumference of the circle, as it serves as a key parameter. The other terms, while related to circle geometry, refer to different aspects; for instance, the radius is half of the diameter, the circumference is the total distance around the circle, and a chord is a line segment whose endpoints lie on the circle but does not necessarily pass through the center. Thus, the diameter specifically identifies the distance across the circle through its center.