open figure

any figure where at least one side does not meet

closed figure

any figure where all sides meet

polygon

any closed, flat figure with straight sides

triangle

any polygon with 3 sides and 3 angles

quadrilateral

any polygon with 4 straight sides

parallelogram

any quadrilateral that has opposite sides that are equal and parallel

rhombus

a parallelogram with 4 sides of equal length

square

parallelogram with 4 right angles and all sides are of equal length

rectangle

a parallelogram with 4 right angles and whose opposite sides are of equal lengh

trapezoid

a quadrilateral with 4 straight sides and 1 set of parallel lines

pentagon

a polygon with 5 sides and 5 angles

hexagon

a polygon with 6 sides and 6 angles

octagon

a polygon with 8 sides and 8 angles