Quadrilaterals
Quadrilaterals are polygons with four sides.
Vocabulary
Adjacent
quadrilateral
symmetry ?
vertex/vertices
The Types of Quadrilaterals with Equal Sides
Square
- Four equal sides or edges
- Four equal angles
Square on point or square on tip
If the shape has four equal sides and four equal angles, it’s a square.
Rhombus
- Four equal sides or edges
- Two pair of equal angles (opposite angles are equivalent)



The plural for rhombus is rhombi because it is originally a Greek word.
Your Turn
Types of Quadrilaterals with Two Pairs of Equal Sides

Rectangles
- Two pair of equal sides
- All four sides are not equal.
Opposite sides are equal.
- All four sides are not equal.
- Two pair of equal angles
Look how a square shape compares to rectangles and rhombi.

The square is the center shape in both lines.

Parallelograms
- Two pair of equal sides. Again, opposite sides are equal.
- Two pair of equal angles or vertices
Kites, Darts or Deltoids
- Two pair of equal sides that are next to or adjacent to one another.
- Two pair of equal angles or vertices

The shape on the left is a kite.
Notice that the tip on the top points out.
This is called a convex surface.
The shape on the right is called a dart or a deltoid.
Notice the tip on the top points inside.
This is called a concave surface.
The two lines that are equal are not opposite to each other. The lines are next to each other. They are called adjacent lines. Adjacent means next to or beside. The top lines that push out and up or in and down are equal adjacent lines.
The longer lower two lines that form a “V” share are also equal adjacent lines.
Types of Quadrilaterals with One Pair of Parallel Lines
Trapezoid
- One pair of parallel lines


Trapezoids are identified by their angles.
Quadrilaterals that are Irregulars also known as (aka) Trapeziums

A Chart about Quadrilaterals
In the left column and the top row, the trapezoids are identified by the size of the inside (interior) angles. Each of these trapezoids have only one pair of parallel sides/edges.
The remaining four shares–square, rectangle, parallelogram, and rhombus–in another group because they each have two pair of parallel sides/edges.

IreWatch this 2:38 video about Types of Quadrilaterals and their Properties by MooMooMath and Science, June 1, 2020.
Summary: