Square

An equal-sided rectangle.

The square of a number $a$ is the product $a\cdot a=a^2$; so called because this product expresses the area of a square with side length $a$.

Comments[edit]

The expression "square" for $a\cdot a$ is (just as "cube" for $a\cdot a\cdot a$) a remnant of the geometric view on numbers of the old Greeks.