What is the circumference of a circle?

The circumference of a circle is defined as the distance around it. This measurement gives you the total length of the perimeter, effectively outlining the circle itself. To calculate the circumference, you can use the formula ( C = \pi d ), where ( d ) is the diameter, or ( C = 2\pi r ), where ( r ) is the radius. This definition clearly indicates that circumference focuses on the outer boundary, distinguishing it as a linear measurement, unlike area, which pertains to the space contained within the circle. The correct choice emphasizes the concept of circumference, making it integral to understanding circle geometry and its properties.