<P> In elementary geometry, a polygon (/ ˈpɒlɪɡɒn /) is a plane figure that is bounded by a finite chain of straight line segments closing in a loop to form a closed polygonal chain or circuit . These segments are called its edges or sides, and the points where two edges meet are the polygon's vertices (singular: vertex) or corners . The interior of the polygon is sometimes called its body . An n - gon is a polygon with n sides; for example, a triangle is a 3 - gon . A polygon is a 2 - dimensional example of the more general polytope in any number of dimensions . </P> <P> The basic geometrical notion of a polygon has been adapted in various ways to suit particular purposes . Mathematicians are often concerned only with the bounding closed polygonal chain and with simple polygons which do not self - intersect, and they often define a polygon accordingly . A polygonal boundary may be allowed to intersect itself, creating star polygons and other self - intersecting polygons . These and other generalizations of polygons are described below . </P>

What do you call a three sided polygon