A square is also a
Rhombus
Parallelogram
A square is a parallelogram because it has opposite pairs of sides parallel and equal.
It is also a rhombus because it has all its sides equal, opposite sides are parallel and the diagonals intersect at 90∘.
A square is also a rectangle because all its angles are 90∘ and its pair of opposite sides are equal and parallel.
A square can't be a trapezium as in trapezium only one of the opposite sides are parallel.