Polygons are closed geometric figuresthat have three or more
straight line segments as sides. Two sides of a polygon are adjacent sides
if they are next to each other and share an angle. Similarly, adjacent angles
are angles that are next to one another, separated only by one side of the
polygon. Polygons have interior anglesat each of their vertices. The more
sides a polygon has, the larger the sum of its interior angles becomes. For
example, the sum of the interior angles of a triangle is 180° and the sum of
a rectangle’s interior angles is 360°. Polygons have diagonals, which are
line segments that connect any two non-adjacentangles.
Naming Polygons
Polygons are named by listing all of their vertices in clockwise or counter-
clockwise order. Polygons are most basically classified by the number of sides
they have. The classification can become more specific based on information
about a polygon’s angles or sides. For example, a regular polygonis equilat-
eral (has all sides of equal length) as well as equiangular (all interior angles are
equal in measure). The following figure is regular octagon ABCDEFGH
(“octa” means eight, so an octagon is an eight-sided polygon).