Rectangle Rectangle Second Sino-Japanese War Category="Quadrilaterals"[image]

In Geometry, a rectangle is 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 four 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.

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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 and a width of 4 would be 20, because 5 × 4 = 20. See the picture above right.

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

Oblong

The word oblong was once commonly used as an alternate name for a rectangle. In his translation of Euclid's Elements, Sir Thomas Heath translates the Greek word ετερομηκες [hetero mekes - literally, "different lengths"] in Book One, Definition 22 as oblong. "Of Quadrilateral figures, a square is that which is both equilateral and right-angled; an oblong that which is right angled but not equilateral...".

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