Explanation

A heptagon is a polygon that has seven sides.

It is a closed figure having 7 vertices.

A heptagon is also sometimes called Septagon.

while

Triangle (3-sided polygon)

Quadrilateral (4-sided polygon)

Pentagon (5-sided polygon)

Hexagon (6-sided polygon)

Heptagon (7-sided polygon)

Octagon ( 8 sided polygon)