Square (Quadrilateral) 
4 sided polygon

A quadrilateral is a  polygon with four vertices or corners, and four edges. There are many different types of quadrilaterals. The  most recognized are squares and rectangles. A square is a rectangle with four edges of the same length and four 90 degree right angles. A rectangle is a four sided quadrilateral with four 90 degree right angles.
The environmental of square: a*4
The area of square a^2=a*a

Using in daily life