Parallelogram - a four-sided figure that has two pairs of parallel sides. Opposite sides are equal in length, and opposite angles are equal as well.
Rectangle - a parallelogram with four right angles.
Rhombus - a parallelogram with four equal sides. See also, Rhombus Area Formula.
Trapezoid - a quadrilateral with one pair of parallel sides.
Kite - a quadrilateral with two pairs of sides that have equal length. The sides with equal length are adjacent to one another, rather than opposite as with a parallelogram.
Square - a rectangle that is also a rhombus. It has four equal sides and four equal angles with a measure of 90 degrees.
Pentagon - a pentagon is a five-sided polygon. A regular pentagon has five equal sides and five equal angles.
Hexagon - a hexagon is a six-sided polygon. See also, Regular Hexagon Area Formula.
Heptagon - a heptagon is a seven-sided polygon.
Octagon - an octagon is an eight-sided polygon. A stop sign is in the shape of a regular octagon since it has eight equal sides and eight equal angles.
Nonagon - a nonagon is a nine-sided polygon.
Decagon - a decagon is a ten-sided polygon.
Regular Polygon - having equal side lengths and equal angles at the vertices.
Convex Polygon - all vertex angles as measured from the interior are less than 180 degrees. Equivalently, all vertex angles measured from the exterior or greater than 180 degrees.