#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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