  ## Encyclopedia > Rectangle

Article Content

# Rectangle

In geometry, a rectangle is a defined as a quadrilateral polygon in which all four angles are right angles.

From this definition, it follows that a rectangle has two pairs of opposite sides of equal length; that is, a rectangle is a parallelogram. A square is a special kind of rectangle where all 4 sides have equal length; that is, a square is both a rectangle and a rhombus. A rectangle that is not a square is colloquially known as an oblong.

Of the two opposite pairs of sides in a rectangle, the length of the longer side is called the length of the rectangle, and the length of the shorter side is called the width. The area of a rectangle is the product of its length and its width; in symbols, A = lw. For example, the area of a rectangle with a length of 5 metres and a width of 4 metres would be 20 square metres, because 5 × 4 = 20. See the picture above.

In calculus, the Riemann integral can be thought of as a limit of sums of the areas of arbitrarily thin rectangles.

All Wikipedia text is available under the terms of the GNU Free Documentation License

Search Encyclopedia
 Search over one million articles, find something about almost anything!

Featured Article
 Thomas a Kempis ... in the British Museum. The Bullingen collection, donated to the city of Cologne in 1838, contained at the time 400 different editions. De Backer (Essai, ut inf.) ...  