Definition
Square
A square is a quadrilateral with four equal sides and four right angles.
What it means
A square must pass two checks: all four sides have the same length, and all four corners are 90°. Turning it so it looks like a diamond does not change either check. A square is also a rectangle and a rhombus because it has the properties of both.
Remember it
Four equal sides plus four 90° corners.
Example
A garden tile has four sides of 12 cm and four right-angle corners. It is a square. Its perimeter is 48 cm, but its size does not affect the shape name.
Watch for
Four equal sides alone make a rhombus, not necessarily a square; the four corners must also be right angles.
Common mix-up
“Square” can also mean a square number or a unit of area. This page owns the geometric shape sense.
Exact meaning
A square is a quadrilateral whose four side lengths are equal and whose four interior angles are right angles.