Question

Why is not the term perimeter used instead of circumference?

Answer 1

Answer:

Both words are used to talk about how long the boundary is of a 2D figure.  Think of circumference as a special case of finding the perimeter.  The term circumference refers to the perimeter of a figure without sides or something like a circle or arc.

So if we were to look at a rectangle and try to determine how long the boundary is we would use perimeter.  On the other hand, if we have a circle we have no way to track how long each side is therefore we use circumference.

Answer 2

Perimeter is a wide term which means the total length of the surrounding (lines ) of the 2D figure.

circumference is the special case of the perimeter in which perimeter of Arc or circular lines are taken in count .