Circumference

The distance around a circle, equal to Pi times the circle's diameter. The formula is written, algebraically, as follows: $\pi \ D$ where D is the circle's diameter.

Alternatively, it can be written as: Failed to parse (MathML with SVG or PNG fallback (recommended for modern browsers and accessibility tools): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 2 \pi\ r } where 'r' is the circle's radius.