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• Quadrilateral

  In Euclidean plane geometry, a quadrilateral, or tetragon is a polygon with four (tetra) edges (or sides) and four vertices or corners. Sometimes, the term quadrangle is used, by analogy with triangle, and tetragon (4-edged) for consistency with original Euclidean terminology and commonly used terms pentagon (5-edged), hexagon (6-edged) and so on. The word "quadrilateral" is derived from the Latin words quadri, a variant of four, and latus, meaning "side". The interior angles of a simple (and planar) quadrilateral ABCD add up to 360 degrees of arc, that is