In geometry, a polygon (/ˈpɒlɪɡɒn/ from the Greek πολύς, polys, “many” and γωνία, gōnia, “angle”) is a plane figure that is described by a finite number of straight-line segments connected to form a closed polygonal chain.
A polygonal (also called polygonal chain, polygonal curve, polygonal circuit, polygonal path or polyline) is a geometric figure consisting of a finite and ordered set of consecutive oriented segments (i.e. such that the second end of a segment coincides with the first end of the next segment and it is the only common point between the two segments) and not adjacent (i.e. such that a segment and subsequent do not belong to the same straight line and not even the first and last segments belong to the same straight line if they have at least one point in common). The segments of the polyline are called sides of the polyline and the ends of the segments are called vertices of the polyline.
A closed polygonal occurs when the last extreme point of the last segment (last extreme) coincides with the first extreme point of the first segment (first extreme). If this condition does not occur then the polygonal is called open. A polygonal is called intertwined, however, if at least two of its non-consecutive segments intersect.