# polygon

A polygon is a closed shape with straight sides. Rectangles, triangles, hexagons, and octagons are all examples of polygons.

The word polygon comes from the Greeks, like most terms in geometry, which they invented. It simply means many (poly) angles (gon). A polygon can’t have any curves or any gaps or openings in its shape. If you want to describe something as angular and closed, like, say, the Pentagon, or a stop sign, you could call it "polygonal."

Definitions of polygon
1

### n a closed plane figure bounded by straight sides

Synonyms:
polygonal shape
Types:
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isogon
an equiangular polygon
convex polygon
a polygon such that no side extended cuts any other side or vertex; it can be cut by a straight line in at most two points
concave polygon
a polygon such that there is a straight line that cuts it in four or more points
a four-sided polygon
triangle, trigon, trilateral
a three-sided polygon
pentagon
a five-sided polygon
hexagon
a six-sided polygon
heptagon
a seven-sided polygon
octagon
an eight-sided polygon
nonagon
a nine-sided polygon
decagon
a polygon with 10 sides and 10 angles
undecagon
an eleven-sided polygon
dodecagon
a twelve-sided polygon
spherical polygon
a figure on the surface of a sphere bounded by arcs of 3 or more great circles
reentering polygon, reentrant polygon
a polygon with one or more reentrant angles
regular polygon
a polygon with all sides and all angles equal
acute triangle, acute-angled triangle
a triangle whose interior angles are all acute
equiangular triangle, equilateral triangle
a three-sided regular polygon
isosceles triangle
a triangle with two equal sides
oblique triangle
a triangle that contains no right angle
obtuse triangle, obtuse-angled triangle
a triangle that contains an obtuse interior angle
right triangle, right-angled triangle
a triangle with one right angle
scalene triangle
a triangle with no two sides of equal length
parallelogram
a quadrilateral whose opposite sides are both parallel and equal in length
trapezium
a quadrilateral with no parallel sides
trapezoid
a quadrilateral with two parallel sides
regular hexagon
a hexagon with six sides of equal length
spherical triangle
a spherical polygon formed by the arcs of 3 great circles
cuneus, wedge, wedge shape
any shape that is triangular in cross section
Type of:
plane figure, two-dimensional figure
a two-dimensional shape