Shape Names
From the triangle a toddler draws to the truncated icosahedron stitched into a soccer ball, shapes have precise names — most of them built from Greek number words. Once you know that penta means five, hexa six and -gon means angle, a 12-sided “dodecagon” stops looking scary.
This list covers 100 shape names: flat 2D polygons, special triangles and quadrilaterals, curved shapes, stars and symbols, and 3D solids, each with a short definition and a real-world example. It’s handy for homework, teaching, design work — and even naming projects. Shapes also sit behind other lists on our site, from constellation names (patterns of stars) to cut styles in our gemstone names.
Polygon names by number of sides
A polygon is a closed flat shape with straight sides. A “regular” polygon has equal sides and angles; the names below apply to any polygon with that many sides.
| Shape | Sides | Where you see it |
|---|---|---|
| Triangle | 3 | Yield signs, roof trusses |
| Quadrilateral | 4 | Any four-sided figure: paper, screens, tiles |
| Pentagon | 5 | The Pentagon building, home plate outline |
| Hexagon | 6 | Honeycomb cells, nuts and bolts |
| Heptagon | 7 | Curved-edge UK 20p and 50p coins |
| Octagon | 8 | U.S. stop signs |
| Nonagon (enneagon) | 9 | Bahá’í houses of worship |
| Decagon | 10 | Some coins and gazebos |
| Hendecagon (undecagon) | 11 | Canadian one-dollar “loonie” coin |
| Dodecagon | 12 | The UK £1 coin since 2017 |
| Tridecagon | 13 | Rare; used in math problems |
| Tetradecagon | 14 | Some decorative tiles |
| Pentadecagon | 15 | Math exercises |
| Hexadecagon | 16 | Some gazebos and bandstands |
| Heptadecagon | 17 | Gauss proved it constructible with compass and straightedge (1796) |
| Octadecagon | 18 | Decorative patterns |
| Enneadecagon | 19 | Rarely used outside geometry |
| Icosagon | 20 | Some coins and pavilions |
| Triacontagon | 30 | Geometry texts |
| Hectogon | 100 | Close to a circle |
| Chiliagon | 1,000 | Descartes used it in philosophy |
| Myriagon | 10,000 | Practically indistinguishable from a circle |
| Apeirogon | Infinitely many | A limit case in advanced geometry |
Types of triangles
Triangles are named by their sides and by their angles — a triangle can be both, like a “right isosceles triangle.”
| Shape | Definition | Example |
|---|---|---|
| Equilateral triangle | All three sides and angles equal (60° each) | Billiard ball rack |
| Isosceles triangle | Two equal sides | A classic A-frame roof |
| Scalene triangle | No equal sides | Irregular sail shapes |
| Right triangle | One 90° angle | A set square; the Pythagorean theorem |
| Acute triangle | All angles under 90° | Pennant flags |
| Obtuse triangle | One angle over 90° | Wide, flat roof gables |
Quadrilateral names
All four-sided shapes are quadrilaterals, but many have their own names. Note: in the U.S. a trapezoid has one pair of parallel sides; British English calls this a trapezium.
| Shape | Definition | Example |
|---|---|---|
| Square | Four equal sides, four right angles | Chessboard squares |
| Rectangle | Four right angles, opposite sides equal | Doors, phones |
| Rhombus | Four equal sides, angles not necessarily 90° | The diamond suit on playing cards |
| Parallelogram | Two pairs of parallel sides | Slanted shadows of rectangles |
| Trapezoid | Exactly one pair of parallel sides (U.S.) | A popcorn bucket in profile |
| Isosceles trapezoid | Trapezoid with equal non-parallel sides | Lampshades in profile |
| Kite | Two pairs of adjacent equal sides | A classic flying kite |
| Dart (arrowhead) | A concave kite | Arrow tips |
| Rhomboid | Parallelogram that is not a rhombus or rectangle | Tilted panels |
| Trapezium | U.S.: no parallel sides; UK: one pair | Meaning depends on country |
Curved and round shape names
Shapes with curves aren’t polygons, but they have precise names too. The crescent even inspired many names that mean moon.
| Shape | Definition | Example |
|---|---|---|
| Circle | All points equal distance from the center | Wheels, coins |
| Ellipse | A stretched circle with two foci | Planetary orbits |
| Oval | Egg-like rounded shape (looser than an ellipse) | Running tracks, eggs |
| Semicircle | Half a circle | Arched windows |
| Crescent | Shape of a thin sliver of the Moon | Croissants, the waxing Moon |
| Annulus | Ring between two concentric circles | Washers, donuts viewed from above |
| Sector | “Pie slice” of a circle | A slice of pizza |
| Segment | Part of a circle cut off by a chord | The flat-bottomed dome of a window |
| Lune | Area between two overlapping circular arcs | Crescent-like math figure |
| Vesica piscis | Lens formed by two overlapping circles | Gothic window tracery, Venn diagrams |
| Reuleaux triangle | Curved triangle of constant width | Some drill bits and guitar picks |
| Stadium | Rectangle with semicircular ends | Running tracks, pill shapes |
| Cardioid | Heart-shaped curve | Cardioid microphone pickup pattern |
| Squircle | Between a square and a circle | Smartphone app icons |
| Spiral | Curve winding around a center | Snail shells, galaxies |
Star, symbol and everyday shape names
Many shapes we use every day are informal but still widely recognized. For the real thing overhead, see our star names.
| Shape | Description | Where you see it |
|---|---|---|
| Pentagram | Five-pointed star drawn in one continuous line | Doodled stars, medieval symbols |
| Hexagram | Six-pointed star of two triangles | Star of David |
| Heptagram | Seven-pointed star | Some sheriff’s badges |
| Octagram | Eight-pointed star | Islamic tile art, Rub el Hizb |
| Heart | Two rounded lobes meeting at a point | Valentine’s cards |
| Diamond | Rhombus standing on its point | Road warning signs |
| Arrow | Line or shaft with a pointed head | Direction signs |
| Chevron | V-shaped stripe | Military rank insignia |
| Cross | Two intersecting bars | Plus signs, flags |
| Trefoil | Three overlapping rings or leaves | Gothic windows, clover |
| Quatrefoil | Four overlapping lobes | Decorative tracery |
| Teardrop | Rounded base tapering to a point | Pendant earrings |
| Star | Any shape with pointed rays | Stickers, badges |
3D shape names
Three-dimensional shapes have volume. Tabletop gamers know several of them as dice — handy if you’re also browsing our dwarf name generator for your next character. The five Platonic solids are the only convex shapes whose faces are identical regular polygons.
| Shape | Faces / description | Example |
|---|---|---|
| Cube | 6 square faces | Dice, sugar cubes |
| Cuboid (rectangular prism) | 6 rectangular faces | Bricks, cereal boxes |
| Sphere | Every surface point equally far from the center | Balls, planets |
| Hemisphere | Half a sphere | Domes, igloos |
| Cylinder | Two circular bases joined by a curved surface | Cans, pipes |
| Cone | Circular base tapering to a point | Ice-cream cones, traffic cones |
| Square pyramid | Square base, 4 triangular faces | The Great Pyramid of Giza |
| Tetrahedron | 4 triangular faces (Platonic) | Four-sided d4 dice |
| Octahedron | 8 triangular faces (Platonic) | d8 dice, diamond crystals |
| Dodecahedron | 12 pentagonal faces (Platonic) | d12 dice |
| Icosahedron | 20 triangular faces (Platonic) | d20 dice |
| Triangular prism | 2 triangles and 3 rectangles | Toblerone box, glass prisms |
| Pentagonal prism | 2 pentagons and 5 rectangles | Some pencils and boxes |
| Hexagonal prism | 2 hexagons and 6 rectangles | Classic pencils, bolts |
| Torus | Donut shape | Donuts, inner tubes |
| Ellipsoid | Stretched sphere | Rugby balls (roughly), some asteroids |
| Spheroid | Ellipsoid with two equal axes | Earth’s actual shape (oblate) |
| Frustum | Cone or pyramid with the top cut off | Lampshades, buckets |
| Capsule | Cylinder with hemispherical ends | Medicine capsules |
| Cuboctahedron | 8 triangles and 6 squares | Architecture and crystal models |
| Truncated icosahedron | 12 pentagons and 20 hexagons | Classic soccer ball, buckyballs |
| Rhombic dodecahedron | 12 rhombus faces | Garnet crystals |
| Möbius strip | Surface with only one side | Recycling-symbol inspiration |
| Pentagonal pyramid | Pentagon base, 5 triangular faces | Some gazebo roofs |
| Hexagonal pyramid | Hexagon base, 6 triangular faces | Tent and turret tops |
| Octagonal prism | 2 octagons and 8 rectangles | Octagonal gift boxes, gazebos |
| Triangular bipyramid | Two tetrahedra joined base to base (6 faces) | Molecule shape of phosphorus pentachloride |
| Pentagonal trapezohedron | 10 kite-shaped faces | d10 dice |
| Truncated tetrahedron | 4 hexagons and 4 triangles | Archimedean solid models |
| Truncated octahedron | 8 hexagons and 6 squares | Fills space with no gaps |
| Stellated octahedron | Two interlocking tetrahedra | Kepler’s <em>stella octangula</em>, star ornaments |
| Great stellated dodecahedron | Star polyhedron with 12 star faces | Kepler–Poinsot solid, paper ornaments |
| Helix | 3D spiral curve at constant slope | DNA, springs, spiral staircases |
How to remember shape names
- Learn the Greek number prefixes. Tri (3), tetra (4), penta (5), hexa (6), hepta (7), octa (8), ennea (9), deca (10), dodeca (12), icosa (20).
- Add the right ending. “-gon” means a flat shape (angles); “-hedron” means a 3D solid (faces). A pentagon is flat; a dodecahedron is solid.
- Link shapes to objects. Octagon = stop sign, hexagon = honeycomb, icosahedron = d20 die.
- Use “n-gon” for big numbers. Mathematicians usually call a 57-sided shape a “57-gon” rather than inventing a Greek name.
- Check the country. Trapezoid and trapezium swap meanings between American and British English — our page uses American usage.
Frequently asked questions
What is a 9-sided shape called?
A nine-sided polygon is called a nonagon or an enneagon (from Greek ennea, nine).
What is an 11-sided shape called?
An 11-sided polygon is a hendecagon, also spelled undecagon. Canada’s one-dollar “loonie” coin is an 11-sided shape.
What is a 12-sided shape called?
A dodecagon. The British £1 coin introduced in 2017 is a dodecagon.
What are the five Platonic solids?
The tetrahedron (4 faces), cube (6), octahedron (8), dodecahedron (12) and icosahedron (20). They are the only convex solids made of identical regular polygons with the same number meeting at each corner.
Is a square a rectangle?
Yes. A square has four right angles, so it meets the definition of a rectangle. It is also a rhombus, because all four sides are equal.
What is the difference between an oval and an ellipse?
An ellipse is a precise mathematical curve with two focal points. “Oval” is a looser everyday word for any egg-like rounded shape, including ellipses.