The Lesson

A trapezoid is a four sided shape with one pair of opposite parallel sides.

a trapezoid or trapezium

Dictionary Definition

The Oxford English Dictionary defines a rectangle as "a quadrilateral figure having only two sides parallel."

Parts of a Trapezoid

  • The parallel sides of a trapezoid are called bases.

    parallel sides of a trapezoid are bases
  • The other sides of a trapezoid are called legs or lateral sides.

    non-parallel sides of a trapezoid are legs

Properties of Trapezoids

  • Only one pair of sides of a trapezoid is parallel.

    one pair of sides of a trapezoid are parallel The other pair of sides is not parallel.

The Perimeter of a Trapezoid

The perimeter of a trapezoid is given by the formula:

perimeter of a trapezoid equals sum of bases and legs In this formula, b1 and b2 are the lengths of the bases of the trapezoid and l1 and l2 are the lengths of the legs of the trapezoid.

The Area of a Trapezoid

The area of a trapezoid is given by the formula:

area of a trapezoid equals half the sum of the bases times the height between them In this formula, b1 and b2 are the lengths of the bases of the trapezoid and h is the height of the trapezoid.
Read more about how to find the area of a trapezoid

Interactive Widget

Here is an interactive widget to help you learn about trapezoids.

Trapezoid, Trapezium

The shape is called a trapezoid in North America. In English speaking countries outside North America, a trapezoid is called a trapezium.

What's in a Name?

Trapezoid and trapezium come from the Greek word "trapezion" meaning 'little table'.

A Trapezoid is a Polygon

A trapezoid is a type of polygon. A polygon is a 2-dimensional shape with straight sides. A trapezoid is an irregular polygon. Irregular polygons have different length sides and different angles.

A Trapezoid is a Quadrilateral

A trapezoid is a quadrilateral. A trapezoid is a four-sided polygon. Parallelograms, rectangles and squares are also quadrilaterals.