A geometric figure consisting of an ordered set of three or more (but a finite number of) points called vertices, each vertex connected by line segments called sides or edges to two other vertices. These two sides are said to be adjacent, and so are any two vertices that are end points of a side. The perimeter of the polygon is the sum of the lengths of the sides. The line segments that join two nonadjacent vertices of a polygon are called diagonals. A polygon is said to be directed, or oriented, if a preferred direction is assigned to each side so that at each vertex one of the adjacent sides is directed toward the vertex and the other away from it.