Trapezium

What is Trapezium ?

Trapezium is (noun) 1. GB a flat four-sided geometric shape, where two of the sides are parallel and the other two sides are not (NOTE: The US term is trapezoid.) 2. US a flat four-sided geometric shape, where none of the sides are parallel (NOTE: The British term is trapezoid.)

 

source: Easier English, Student Dictionary Upper Intermediate Level