Quadrilaterals & Polygons
Move from quadrilaterals into the wider world of polygons, regular figures, concavity, and angle-sum rules.
21 concepts in this topic
These pages connect shape names to the properties that define them, so you can read polygons by structure rather than by rough appearance alone.
Parallelogram
A parallelogram is a quadrilateral with both pairs of opposite sides parallel.
Rectangle
A rectangle is a parallelogram with four right angles.
Rhombus
A rhombus is a quadrilateral with four equal sides.
Square
A square has four equal sides and four right angles.
Trapezoid
A trapezoid has at least one pair of parallel sides.
Isosceles Trapezoid
An isosceles trapezoid has equal legs and one pair of parallel sides.
Kite
A kite has two pairs of adjacent equal sides.
Convex Polygon
A convex polygon has all interior angles less than 180 degrees.
Concave Polygon
A concave polygon has at least one interior angle greater than 180 degrees.
Regular Polygon
A regular polygon has equal side lengths and equal angles.
Irregular Polygon
An irregular polygon does not have all sides and angles equal.
Pentagon
A pentagon is a polygon with five sides.
Hexagon
A hexagon is a polygon with six sides.
Heptagon
A heptagon is a polygon with seven sides.
Octagon
An octagon is a polygon with eight sides.
Nonagon
A nonagon is a polygon with nine sides.
Decagon
A decagon is a polygon with ten sides.
Dodecagon
A dodecagon is a polygon with twelve sides.
n-gon
An n-gon is a polygon described by a general number of sides n.
Interior Angle Sum
The interior angle sum of an n-gon is (n minus 2) times 180 degrees.
Exterior Angle Sum
The exterior angles of a polygon always add to 360 degrees.