The square is:
-A polygon, that is a part of the plane bounded by a closed broken line;
-A regular polygon since it has 4 sides and 4 congruent angles;
-A parallelogram, i.e. a quadrilateral with opposite sides parallel.
It has 4 congruent sides; the opposite sides are parallel; consecutive sides are perpendicular.
It has 2 equal and perpendicular diagonals: intersecting they divide in half; they are bisectors of the angles; divide the square into 4 congruent isosceles right triangles.
It has equal angles of 90 °; the sum of the internal and external angles is always 360 °.
AXES OF SYMMETRY:
It has 4 axes of symmetry, two passing for the diagonals and two for the midpoints of the opposite sides.