Classifying Quadrilaterals

A quadrilateral is any 2D shape with exactly four straight sides and four angles. But not all quadrilaterals are the same! We can sort, or classify, them by looking closely at their sides and angles.

Types of Quadrilaterals

Here are the most common members of the quadrilateral family:

1. Parallelogram A parallelogram has two pairs of parallel sides. That means the opposite sides will never touch, no matter how far you stretch them. The opposite sides are also equal in length.

2. Rectangle A rectangle is a special parallelogram. It has four right angles (perfect corners that look like an "L", measuring exactly $90^\circ$). Because it is a parallelogram, its opposite sides are parallel and equal.

3. Rhombus A rhombus is another special parallelogram. It has four equal sides. Think of it like a slanted square or a diamond shape!

4. Square A square is the most special quadrilateral of all. It has four equal sides AND four right angles. Because of this, a square is actually a type of rectangle and a type of rhombus!

5. Trapezoid A trapezoid is a little different from the others. It has exactly one pair of parallel sides. The other two sides are not parallel.

Tricky Quadrilateral Questions

Sometimes, shapes can have more than one name because they fit into multiple categories. Let's look at a few common questions:

• Is a square also a rectangle? Yes! To be a rectangle, a shape just needs four right angles. A square has four right angles, so it is a special type of rectangle.
• Name all quadrilaterals with 4 equal sides: Both a rhombus and a square have four equal sides.
• Which quadrilateral has exactly 1 pair of parallel sides? A trapezoid is the only quadrilateral with exactly one pair of parallel sides.