Square:

A quadrilateral is a plane figure bounded via four intersecting straight lines.

(a) A square is a quadrilateral whether all the sides are equal and the angles are at right angles.

(b) A parallelogram is a quadrilateral whether the opposite sides are parallel.

(c)  A rectangle is a quadrilateral whether the opposite sides are equal and all the angles are at right angles.

(d) A rhombus is a quadrilateral whether all the sides are equal and the angles are not at right angles. Conversely whether this case, the opposite angles are equivalent as in diagram (a).

(e) A rhomboid is a quadrilateral whether the opposite sides are equal although the angles are not at right angles to each other diagram (b).

(f)  A trapezoid is a quadrilateral whether only two sides are parallel to each other as depicted in diagram (c).

(g) A trapezium is a quadrilateral whether no side is parallel to each other but may have two pairs of adjacent sides equal. It is also known as kite diagram (d).