Final answer:
The line segment that passes through the center of a circle and has both endpoints on the circle is called a diameter.
Step-by-step explanation:
The line segment which passes through the center of a circle and has both endpoints on the circle is called a diameter.
A diameter is the longest chord in a circle and it divides the circle into two equal halves. It passes through the center, and any point on the circumference of the circle is equidistant from the center.
For example, in the circle below, AB is a diameter: