The characteristics of triangles squares rectangles parallelograms quadrilaterals pentagons hexagons and octogons?

Squares, rectangles, and parallelograms all fall under the category of "quadrilateral" simply because they all have four sides; however, quadrilaterals must also be two-dimensional, and all of its sides must be straight. Squares must have four equilateral sides--with opposite sides parallel to each other-- and each angle must be a right angle (90 degrees). Rectangles are like squares in that each angle must be a right angle, and opposite sides must be parallel, but all four sides need not be equal to each other in length; rather, only opposite sides are equal in length. Parallelograms must have opposite sides that are equal in length and parallel to each other, as well as opposite angles that are equal to each other, but these angles are not right angles. Triangles, pentagons, hexagons, and octagons all fall under the category of "polygon" because they are two-dimensional figures made of straight lines, but do not have four sides like quadrilaterals. Triangles must have three sides and three angles that add up to 180 degrees. Pentagons have five sides, hexagons have six sides, and octagons have eight sides.