Definition:Quadrilateral/Oblong

Definition

An oblong is a quadrilateral whose angles are all right angles, but whose sides are not all the same length:

Also known as

The word oblong is rarely seen nowadays.

Rectangle is the term usually used instead, unless it is essential to emphasise that such a quadrilateral is not a square.

Euclid's Definitions

In the words of Euclid:

Of quadrilateral figures, a square is that which is both equilateral and right-angled; an oblong that which is right-angled but not equilateral; a rhombus that which is equilateral but not right-angled; and a rhomboid that which has its opposite sides equal to one another but is neither equilateral nor right-angled. And let quadrilaterals other than these be called trapezia.

(The Elements: Book $\text{I}$: Definition $22$)

Also see

• Results about oblongs can be found here.

Sources

• 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): oblong
• 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): oblong