What term describes a straight line from the center to the circumference of a circle or sphere?

The term that describes a straight line from the center to the circumference of a circle or sphere is "radius." The radius is a fundamental concept in geometry related to circles and spheres, as it represents the distance from the center point of the shape to any point on its boundary. This measurement is critical in various calculations involving circles, including finding the area or circumference.

The diameter, while closely related, specifically refers to a line that passes through the center of the circle and connects two points on the circumference, representing twice the length of the radius. The circumference refers to the distance around the circle itself, and a chord is any line segment whose endpoints both lie on the circumference but does not necessarily pass through the center. Understanding the definitions and relationships of these terms is essential for solving geometry problems involving circles.