Vocab

Radius-(r) The distance from any point on the circle to the center.

Diameter-(d) The distance across a circle through the center.

Circumference-(C) The distance around the outside of a circle.
To find the circumference
C=pi✖️d
OR
C=2✖️pi✖️r
Pi-A ratio comparing circumference to diameter.(also known as 3.14 or 22/7)