# How to Learn Quadrilateral Shapes

By Jon Zamboni
LaureniFochetto/iStock/Getty Images

A *quadrilateral* is a two-dimensional shape made of four straight lines that connect in four *vertices*, or corners. Quadrilaterals go by different names, depending on the size of their angles and the properties of their sides. **Squares, parallelograms, and trapezoids are all common forms of quadrilaterals.**

## Squares and Rectangles

Squares are one of the most familiar forms of quadrilaterals. A square has four sides of equal length. In addition, each of a square's four corners is a 90-degree angle. Opposite sides of a square are parallel to each other.

Like a square, a rectangle's opposite sides are parallel, and its corners are all 90-degree angles. However, not all of a rectangle's sides are of equal length. Any two opposite sides of a rectangle are equal, but two neighboring, or adjacent, sides of a rectangle have different lengths.

## Rhombuses and Parallelograms

Diamond-shaped rhombuses have a great deal in common with squares -- all four of a rhombus's sides have equal length, and its opposite sides are parallel to each other. However, there is one important difference. None of a rhombus's angles are 90 degrees. Any two opposite corners of a rhombus have equal angles.

A parallelogram is to a rectangle as a rhombus is to a square. As the name suggests, opposite sides of a parallelogram are parallel to each other. Opposite sides also have equal lengths; however, the adjacent sides of a parallelogram have unequal lengths. Like a rhombus, any two opposite corners of a parallelogram have equal angles.

## Trapezoids and Kites

Not all quadrilaterals are completely parallel. A trapezoid has only one pair of parallel sides, which are of unequal length. The other two sides of a trapezoid are not parallel, though they may be of equal length.

A kite has no parallel sides. Instead, a kite has two pairs of sides with equal length. The equal sides of a kite are adjacent to each other, rather than opposite from each other. The two corners where the kite's unequal lines meet are opposite each other, and are equal angles.