Quadrilateral types and names | Tangente

Getting to know quadrilaterals

For the familiar convex quadrilaterals, the classification criteria are, first, whether the sides are parallel, then whether their lengths are equal, and finally whether there are any right angles.

Written by

Jean-Jacques Dupas

PublishedNovember 21, 2024UpdatedMay 16, 20261 min read

A quadrilateral with four sides of different lengths is called a scalene quadrilateral.

Scalene quadrilateral (trapezium).

If exactly one pair of opposite sides is parallel, the quadrilateral is called a trapezoid. Used (yet again!) by Charles de Bovelles in 1542, the term comes from the Latin trapezium, meaning "small table" and alluding to the tabletop being parallel to the ground. A trapezoid may also be isosceles, when its two non-parallel sides have the same length, or a right trapezoid. Be warned: a trapezium is a scalene quadrilateral.

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