Quadrilateral

any geometric shape that has four sides, e.g., a rectangle, square, kite, parallelogram, rhombus.

Taken from Dictionary of Science

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In geometry, a quadrilateral is a polygon with four 'sides' or edges and four vertices or corners. Sometimes, the term quadrangle is used, for analogy with triangle, and sometimes tetragon for consistency with pentagon (5-sided), hexagon (6-sided) and so on. The word quadrilateral is made of the words quad and lateral. Quad means four and lateral means sides. The interior angles of a quadrilateral add up to 360 degrees of arc.

Quadrilaterals are simple (not self-intersecting) or complex (self-intersecting). Simple quadrilaterals are either convex or concave.

All convex quadrilaterals tile the plane by repeated rotation around the midpoints of their edges.

Taken from Wikipedia