<P> In geometry, a heptagon is a seven - sided polygon or 7 - gon . </P> <P> The heptagon is also occasionally referred to as the septagon, using "sept -" (an elision of septua -, a Latin - derived numerical prefix, rather than hepta -, a Greek - derived numerical prefix) together with the Greek suffix "- agon" meaning angle . </P> <P> A regular heptagon, in which all sides and all angles are equal, has internal angles of 5π / 7 radians (128 ​ ⁄ degrees). Its Schläfli symbol is (7). </P> <P> The area (A) of a regular heptagon of side length a is given by: </P>

Size of each interior angle of a regular heptagon