A square has four equal sides and four right angles. It is both a rectangle and a rhombus. The area is side squared (s²). The perimeter is 4s. The diagonal is s√2.

Squares have perfect symmetry: four lines of symmetry and rotational symmetry of order four. They tile the plane without gaps. In geometry, the square is a regular polygon with four sides.

Squares appear in grids, tiles, and city blocks. In algebra, completing the square transforms quadratic expressions. In statistics, chi-square tests use squared deviations. The shape is simple but deeply embedded in mathematics and design.

• Four equal sides and four right angles
• Area = s²; perimeter = 4s
• Diagonal = s√2
• Regular polygon with four sides