The Rectangle: A rectangle is a quadrilateral that has four right angles. The opposite sides are parallel.
A rhombus is a four-sided shape where all sides have equal length.
Also opposite sides are parallel and opposite angles are equal.
Another interesting thing is that the diagonals (dashed lines in second figure) of a rhombus bisect each other at right angles.
A square has equal sides and every angle is a right angle (90°)
Also opposite sides are parallel.
Opposite sides are parallel and equal in length, and opposite angles are equal (angles "a" are the same, and angles "b" are the same)
It is called an Isosceles trapezoid if the sides that aren't parallel are equal in length and both angles coming from a parallel side are equal, as shown.
Language Note: In the US a "trapezium" is a quadrilateral with NO parallel sides!