#parallelogram  a quadrilateral whose opposite sides are both parallel and equal in length
  exclusion:  #trapezium
  supertype:  #quadrilateral__quadrangle__tetragon  a four-sided polygon
  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"

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