What is a trapezium?

A trapezium is a four-sided shape with exactly one pair of parallel sides. The parallel sides are called the bases and the other two are the legs. In the United States the same shape is called a trapezoid, and confusingly the word trapezium there means a quadrilateral with no parallel sides at all, so check which convention a book or worksheet is using.

Examples

• A shape with a top side of 4 cm, a bottom side of 8 cm and two slanted sides is a trapezium.
• A trapezium whose two legs are equal is an isosceles trapezium.
• Area of a trapezium: half the sum of the parallel sides, times the height.

Quick facts

• UK, Australia and New Zealand say trapezium; the United States says trapezoid.
• A trapezium is not a parallelogram, because only one pair of sides is parallel.
• The two angles on each leg add up to 180°.