The equator and all lines of longitude are called great circles because the represent the circumference of the earth. The other latitude lines along the globe are smaller then the actually circumference.
circumference = 2*pi*radius or pi*diameter
It is an arc
An arc
The circumference of a circle = pi*diametre = 2pi*radius
Then they are similar.
Pi times the diameter of a circle gives its circumference.
The ratio of the circumference of a circle to its diameter is Pi. (3.14159)
The planet with the largest circumference is Jupiter. About its equator, the circumference measure about 449,197 kilometers. Jupiter is an outer planet that also is the largest in the solar system.
The equator, around Earth's total circumference as a sphere.
Any circle's circumference can be calculated with the formula 2(pi)*radius
Circumference is a special name for a circles perimeter. I think the answer you are looking for is radious.