The perimeter of a circle is called the circumference. It represents the total distance around the edge of the circle.
To calculate the circumference, you can use the formula:
C = 2πr
where C is the circumference, π (pi) is approximately 3.14159, and r is the radius of the circle. Alternatively, if you know the diameter (the distance across the circle through its center), you can also use the formula:
C = πd
where d is the diameter. This relationship shows how the circumference relates to the diameter, highlighting the importance of the constant π in circle geometry.