A rectangle is a four-sided shape where every angle is a right angle (90°). Also opposite sides are parallel and of equal length. 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) meet in the middle at a right angle. In other words they bisect (cut in half) each other at right angles.