What is the term for the line running through the center of a circle connecting two points?

The term for the line running through the center of a circle connecting two points is known as the diameter. The diameter is a specific type of chord that passes through the center of the circle, making it the longest possible chord in that circle. It essentially divides the circle into two equal halves and is always twice the length of the radius, which is the distance from the center of the circle to any point on its perimeter.

The other terms listed are related but have distinct definitions: the radius refers to any line segment from the center of the circle to its perimeter and is half the length of the diameter. Circumference is the total distance around the circle, not a line segment, and a chord is any line segment that connects two points on the circle but does not necessarily pass through the center. Thus, the diameter is the only term that fits the description given in the question.