The classification schemes taught in elementary school involve the number of pairs of parallel sides, and the congruence of sides, and whether or not all the angles are right angles (all angles are congruent). Quadrilaterals can be classified by whether or not their sides, angles, diagonals, or vertices have special properties. Like all polygons that have more than three sides, quadrilaterals can be convex like these, ,, or concave like these. Just as triangles and quadrilaterals are special types of polygons, there are many subclasses of quadrilaterals. Lateral means “side” (think of football, for example). Quadri- (four) + -lateral (side) means “four-sided.”Ĭompare quadri- to Spanish cuatro. squares ( B), the most special of them all.rhombuses ( C and D are the “typical” examples, but all squares also fit the definition of rhombuses).rectangles ( F is the “typical” example, but all squares also fit the definition of rectangles).parallelograms ( E is the “typical” example, but all rectangles and rhombuses also fit the definition of parallelograms).trapezoids ( A and J are “typical” examples, but all parallelograms also fit the definition of trapezoids).
See the articles on each type for their definitions and special properties. Most of the time, context will make clear what you mean, but you should remain aware that in some cases you may need to clarify.Įlementary school curricula typically have children learn the names of special subsets of quadrilaterals with particular features. The usual definitions of polygons, however, refer only to the line segments that form the edges of the polygon. When we talk about “dissecting” a parallelogram and rearranging the parts to form a rectangle in order to determine the area of the parallelogram, we are clearly referring to the edges and the interior. (This also means that a quadrilateral has exactly four vertices, and exactly four angles.)ĭiscussions of 2-D shapes sometimes refer only to the boundary (the line segments that form the edges of the figure) or to the interior as well. (This also means that a quadrilateral has exactly four vertices, and exactly four angles.) MeaningĪ quadrilateral is a polygon that has exactly four sides. So all other quadrilaterals are irregular.A quadrilateral is a polygon that has exactly four sides. The only regular (all sides equal and all angles equal) quadrilateral is a square. and that's it for the special quadrilaterals. one of the diagonals bisects (cuts equally in half) the other.
The RhombusĪ rhombus is a four-sided shape where all sides have equal length (marked "s").Īlso opposite sides are parallel and opposite angles are equal.Īnother interesting thing is that the diagonals (dashed lines) meet in the middle at a right angle. The SquareĪ square has equal sides (marked "s") and every angle is a right angle (90°)Ī square also fits the definition of a rectangle (all angles are 90°), and a rhombus (all sides are equal length). The little squares in each corner mean "right angle"Ī rectangle is a four-sided shape where every angle is a right angle (90°).Īlso opposite sides are parallel and of equal length. Let us look at each type in turn: The Rectangle
Some types are also included in the definition of other types! For example a square, rhombus and rectangle are also parallelograms. There are special types of quadrilateral: They should add to 360° Types of Quadrilaterals Try drawing a quadrilateral, and measure the angles. interior angles that add to 360 degrees:.(Also see this on Interactive Quadrilaterals) Properties
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