#polygon__polygonal_shape__polygonalshape  a closed plane figure bounded by straight sides
  supertype:  plane_figure__planefigure__two-dimensional_figure__twodimensionalfigure  a two-dimensional shape
  subtype:  convex_polygon  a polygon such that no side extended cuts any other side or vertex; it can be cut by a line in at most two points
  subtype:  concave_polygon__concavepolygon  a polygon such that there is a straight line that cuts it in four or more points
     subtype:  reentrant_polygon__reentrantpolygon__reentering_polygon  a polygon with one or more reentrant angles
  subtype:  regular_polygon  a polygon with all sides and all angles equal
     subtype:  equilateral_triangle__equilateraltriangle__equiangular_triangle__equiangulartriangle  a three-sided regular polygon
  subtype:  quadrilateral__quadrangle__tetragon  a four-sided polygon
     subtype:  parallelogram  a quadrilateral whose opposite sides are both parallel and equal in length
        subtype:  rhombus__rhombu__rhomb  a parallelogram with four equal sides; an oblique-angled equilateral parallelogram
        subtype:  rhomboid  a parallelogram with adjacent sides of unequal lengths; an oblique-angled parallelogram with only the opposite sides equal
        subtype:  rectangle  a parallelogram with four right angles
           subtype:  square__foursquare  (geometry) a plane rectangle with four equal sides and four right angles; a four-sided regular polygon; "you can compute the area of a square if you know the length of its sides"
              subtype:  quadrate  a square-shaped object
           subtype:  box.rectangle  a rectangular drawing; "the flowchart contained many boxes"
     subtype:  trapezium  (in US) a quadrilateral with no parallel sides
     subtype:  trapezoid  (in US) a quadrilateral with two parallel sides
  subtype:  trigon__triangle__trilateral  a three-sided polygon
     subtype:  acute_triangle__acutetriangle__acute-angled_triangle  a triangle whose interior angles are all acute
     subtype:  equilateral_triangle__equilateraltriangle__equiangular_triangle__equiangulartriangle  a three-sided regular polygon
     subtype:  isosceles_triangle__isoscelestriangle  a triangle with two equal sides
     subtype:  oblique_triangle__obliquetriangle  a triangle that contains no right angle
     subtype:  obtuse_triangle__obtuse-angled_triangle  a triangle that contains an obtuse interior angle
     subtype:  right_triangle__righttriangle__right-angled_triangle  a triangle with one right angle
     subtype:  scalene_triangle__scalenetriangle  a triangle with no two sides of equal length
     subtype:  wedge_shape__wedgeshape__wedge__cuneus  any shape that is triangular in cross section
  subtype:  pentagon  a five-sided polygon
  subtype:  hexagon  a six-sided polygon
  subtype:  heptagon  a seven-sided polygon
  subtype:  octagon  an eight-sided polygon
  subtype:  nonagon  a nine-sided polygon
  subtype:  decagon  a polygon with 10 sides and 10 angles
  subtype:  undecagon  an eleven-sided polygon
  subtype:  dodecagon  a twelve-sided polygon
  subtype:  spherical_polygon__sphericalpolygon  a figure on the surface of of sphere bounded by arcs of 3 or more great circles
     subtype:  spherical_triangle__sphericaltriangle  a spherical polygon formed by the arcs of 3 great circles

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