Circumference is the distance around the outside of a circle (its perimeter!). Want a review of circle vocabulary terms (like pi, radius, and diameter)? ... of a circle with a diameter of 3 \greenD3 3start color greenD, 3, end color greenD. .... Suppose the radius of a circle is 5 \purpleD{5} 5start color purpleD, 5, end color purpleD