The different parts of a quadrilateral and their definitions: side, angle, vertex, base, height, diagonal, perimeter, and area.

What are the parts of a quadrilateral?

Learn about the parts of a quadrilateral, with definitions and diagrams, in this short video.

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The size of the surface covered by a quadrilateral is called its area.

Each of the line segments that form the quadrilateral’s boundaries is called a side. A quadrilateral has four sides.

Sides that share an endpoint are called adjacent sides.

Sides that don’t share an endpoint are called opposite sides.

The total length of the four sides is called the perimeter.

The point where two sides meet is called a vertex. A quadrilateral has four vertices.

An imaginary line joining two opposite vertices is called a diagonal.

The angle formed by two adjacent sides is called an interior angle (or, simply, an angle). A quadrilateral has four angles.

The side upon which the quadrilateral is resting is called its base.

The length of a perpendicular line from the base to the side opposite the base is called the height.

Can you now identify the parts of a quadrilateral? Reinforce your learning with the worksheet below.

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