# Square

A square is a **rectangle** with all sides equal. A square with side *a* has perimeter 4*a* and area *a*^{2}.

The square is used as the unit of area; that is, a figure's area is expressed as the number of equal squares of some standard, such as square inches or square meters, that the figure can contain. In Greek **geometry**, the area of a figure was determined by converting the figure to a square of the same area. This is easily accomplished for triangles, rectangles, and other **polygons**, but is often impossible for other figures, such as circles.

## Additional topics

Science EncyclopediaScience & Philosophy: *Spectroscopy* to *Stoma (pl. stomata)*