In geometry, a quadrilateral is a polygon with four sides or edges. There are several polygons that share the characteristics of a quadrilateral. However, while at least six shapes can be considered quadrilaterals, only two have four right angles -- rectangles and squares.

## Properties of Quadrilaterals

Quadrilateral quite literally means “four sides.” It can refer to any mathematical shape that is made up of four edges and four corners; however, the edges must be straight lines. Another property of a quadrilateral is that the sum of the interior angles must equal 360 degrees. As long as a shape fits within these parameters, it can be considered a quadrilateral.

## Rectangles

A rectangle is one kind of quadrilateral with four right angles. The definition of a rectangle is a shape with four sides and four right angles. This means each angle in a rectangle measures 90 degrees. Another property of a rectangle is that opposite sides are parallel to each other and equal in length.

## Squares

A square is the other type of quadrilateral with four right angles. The definition of a square is a shape with four equal sides and four right angles. A square is distinguished from a rectangle in that every side of a square is equal in length. Opposite sides are also parallel to each other.

## Other Types of Quadrilaterals

There are several other shapes that fit the parameters of a quadrilateral, though they do not have four right angles. A parallelogram is a simply a quadrilateral with parallel opposite sides. Different from a rectangle, a parallelogram does not have to have four right angles. A rhombus is a quadrilateral where all four sides are equal in length. Different from a square, a rhombus does not have to have four right angles. A trapezoid is a shape with only one pair of opposite parallel sides.

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