In geometry, a polygon is traditionally a plane figure that is bounded by a finite chain of straight line segments closing in a loop to form a closed chain. These segments are called its edges or sides, and the points where two of the edges meet are the polygon's vertices (singular: vertex) or corners.

The word polygon comes from Late Latin polygōnum (a noun), from Greek πολύγωνον (polygōnon/polugōnon), noun use of neuter of πολύγωνος (polygōnos/polugōnos, the masculine adjective), meaning "many-angled". Individual polygons are named (and sometimes classified) according to the number of sides, combining a Greek-derived numerical prefix with the suffix -gon, e.g. pentagon, dodecagon. The triangle, quadrilateral and nonagon are exceptions, although the regular forms trigon, tetragon, and enneagon are sometimes encountered as well.

## Greek numbers

Polygons are primarily named by prefixes from Ancient Greek numbers.

English-Greek numbers[1][2]
English cardinal number English ordinal number Greek cardinal number Greek ordinal number
one first heis (fem. mia, neut. hen) protos
two second duo deuteros
three third treis tritos
four fourth tettares tetartos
five fifth pente pemptos
six sixth hex hektos
seven seventh hepta hebdomos
eight eighth okto ogdoös
nine ninth ennea enatos
ten tenth deka dekatos
eleven eleventh hendeka hendekatos
twelve twelfth dodeka dodekatos
thirteen thirteenth triskaideka dekatotritos
fourteen fourteenth tettareskaideka dekatotetartos
fifteen fifteenth pentekaideka dekatopemptos
sixteen sixteenth hekkaideka dekatohektos
seventeen seventeenth heptakaideka dekatohebdomos
eighteen eighteenth oktokaideka dekatoögdoös
nineteen nineteenth enneakaideka dekatoënatos
twenty twentieth eikosi eikostos
twenty-one twenty-first heiskaieikosi eikostoprotos
twenty-two twenty-second duokaieikosi eikostodeuteros
twenty-three twenty-third triskaieikosi eikostotritos
twenty-four twenty-fourth tetterakaieikosi eikostotetartos
twenty-five twenty-fifth pentekaieikosi eikostopemptos
twenty-six twenty-sixth hekkaieikosi eikostohektos
twenty-seven twenty-seventh heptakaieikosi eikostohebdomos
twenty-eight twenty-eighth oktokaieikosi eikostoögdoös
twenty-nine twenty-ninth enneakaieikosi eikostoënatos
thirty thirtieth triakonta triakostos
thirty-one thirty-first heiskaitriakonta triakostoprotos
forty fortieth tessarakonta tessarakostos
fifty fiftieth pentekonta pentekostos
sixty sixtieth hexekonta hexekostos
seventy seventieth hebdomekonta hebdomekostos
eighty eightieth ogdoëkonta ogdoëkostos
ninety ninetieth enenekonta enenekostos
hundred hundredth hekaton hekatostos
hundred and ten hundred and tenth dekakaihekaton hekatostodekatos
hundred and twenty hundred and twentieth ikosikaihekaton hekatostoikostos
two hundred two hundredth diakosioi diakosiostos
three hundred three hundredth triakosioi triakosiostos
four hundred four hundredth tetrakosioi tetrakosiostos
five hundred five hundredth pentakosioi pentakosiostos
six hundred six hundredth hexakosioi hexakosiostos
seven hundred seven hundredth heptakosioi heptakosiostos
eight hundred eight hundredth oktakosioi oktakosiostos
nine hundred nine hundredth enneakosioi enneakosiostos
thousand thousandth chilioi chiliostos
two thousand two thousandth dischilioi dischiliostos
three thousand three thousandth trischilioi trischiliostos
four thousand four thousandth tetrakischilioi tetrakischiliostos
five thousand five thousandth pentakischilioi pentakischiliostos
six thousand six thousandth hexakischilioi hexakischiliostos
seven thousand seven thousandth heptakischilioi heptakischiliostos
eight thousand eight thousandth oktakischilioi oktakischiliostos
nine thousand nine thousandth enneakischilioi enneakischiliostos
ten thousand ten thousandth myrioi myriastos
twenty thousand twenty thousandth dismyrioi dismyriastos
thirty thousand thirty thousandth trismyrioi trismyriastos
forty thousand forty thousandth tetrakismyrioi tetrakismyriastos
fifty thousand fifty thousandth pentakismyrioi pentakismyriastos
sixty thousand sixty thousandth hexakismyrioi hexakismyriastos
seventy thousand seventy thousandth heptakismyrioi heptakismyriastos
eighty thousand eighty thousandth oktakismyrioi oktakismyriastos
ninety thousand ninety thousandth enneakismyrioi enneakismyriastos
hundred thousand hundred thousandth dekakismyrioi dekakismyriastos
two hundred thousand two hundred thousandth ikosakismyrioi ikosakismyriastos
three hundred thousand three hundred thousandth triakontakismyrioi triakontakismyriastos
million millionth hekatontakismyrioi hekatontakismyriastos
two million two millionth diakosakismyrioi diakosakismyriastos
three million three millionth triakosakismyrioi triakosakismyriastos
ten million ten millionth chiliakismyrioi chiliakismyriastos
hundred million hundred millionth myriakismyrioi myriakismyriastos

## Systematic polygon names

To construct the name of a polygon with more than 20 and fewer than 100 edges, combine the prefixes as follows. The "kai" connector is not included by some authors.

Tens and Ones final suffix
-kai- 1 -hena- -gon
20 icosi- (icosa- when alone) 2 -di-
30 triaconta- 3 -tri-
40 tetraconta- 4 -tetra-
50 pentaconta- 5 -penta-
60 hexaconta- 6 -hexa-
70 heptaconta- 7 -hepta-
80 octaconta- 8 -octa-
90 enneaconta- 9 -ennea-

Extending the system up to 999 is expressed with these prefixes.[3]

Polygon names
Ones Tens Twenties Thirties+ Hundreds
10 deca- 20 icosa- 30 triaconta-
1 hena- 11 hendeca- 21 icosi-hena- 31 triaconta-hena- 100 hecta-
2 di- 12 dodeca- 22 icosi-di- 32 triaconta-di- 200 dihecta-
3 tri- 13 triskaideca- 23 icosi-tri- 33 triaconta-tri- 300 trihecta-
4 tetra- 14 tetrakaideca- 24 icosi-tetra- 40 tetraconta- 400 tetrahecta-
5 penta- 15 pentakaideca- 25 icosi-penta- 50 pentaconta- 500 pentahecta-
6 hexa- 16 hexakaideca- 26 icosi-hexa- 60 hexaconta- 600 hexahecta-
7 hepta- 17 heptakaideca- 27 icosi-hepta- 70 heptaconta- 700 heptahecta-
8 octa- 18 octakaideca- 28 icosi-octa- 80 octaconta- 800 octahecta-
9 ennea- 19 enneakaideca- 29 icosi-ennea- 90 enneaconta- 900 enneahecta-

## List of n-gons by Greek numerical prefixes

List of n-gon names[4][5]
Sides Names
1 henagon monogon
2 digon bigon
3 trigon triangle
5 pentagon
6 hexagon
7 heptagon septagon
8 octagon
9 enneagon nonagon
10 decagon
11 hendecagon undecagon
12 dodecagon
13 tridecagon triskaidecagon
20 icosagon
21 icosikaihenagon icosihenagon
23 icosikaitrigon icositrigon icosatrigon
24 icosikaitetragon icositetragon icosatetragon
25 icosikaipentagon icosipentagon icosapentagon
26 icosikaihexagon icosihexagon icosahexagon
27 icosikaiheptagon icosiheptagon icosaheptagon
28 icosikaioctagon icosioctagon icosaoctagon
29 icosikaienneagon icosienneagon icosaenneagon
30 triacontagon
31 triacontakaihenagon triacontahenagon tricontahenagon
33 triacontakaitrigon triacontatrigon tricontatrigon
34 triacontakaitetragon triacontatetragon tricontatetragon
35 triacontakaipentagon triacontapentagon tricontapentagon
36 triacontakaihexagon triacontahexagon tricontahexagon
37 triacontakaiheptagon triacontaheptagon tricontaheptagon
38 triacontakaioctagon triacontaoctagon tricontaoctagon
39 triacontakaienneagon triacontaenneagon tricontaenneagon
40 tetracontagon tessaracontagon
41 tetracontakaihenagon tetracontahenagon tessaracontahenagon
43 tetracontakaitrigon tetracontatrigon tessaracontatrigon
44 tetracontakaitetragon tetracontatetragon tessaracontatetragon
45 tetracontakaipentagon tetracontapentagon tessaracontapentagon
46 tetracontakaihexagon tetracontahexagon tessaracontahexagon
47 tetracontakaiheptagon tetracontaheptagon tessaracontaheptagon
48 tetracontakaioctagon tetracontaoctagon tessaracontaoctagon
49 tetracontakaienneagon tetracontaenneagon tessaracontaenneagon
50 pentacontagon pentecontagon
51 pentacontakaihenagon pentacontahenagon pentecontahenagon
53 pentacontakaitrigon pentacontatrigon pentecontatrigon
54 pentacontakaitetragon pentacontatetragon pentecontatetragon
55 pentacontakaipentagon pentacontapentagon pentecontapentagon
56 pentacontakaihexagon pentacontahexagon pentecontahexagon
57 pentacontakaiheptagon pentacontaheptagon pentecontaheptagon
58 pentacontakaioctagon pentacontaoctagon pentecontaoctagon
59 pentacontakaienneagon pentacontaenneagon pentecontaenneagon
60 hexacontagon hexecontagon
61 hexacontakaihenagon hexacontahenagon hexecontahenagon
63 hexacontakaitrigon hexacontatrigon hexecontatrigon
64 hexacontakaitetragon hexacontatetragon hexecontatetragon
65 hexacontakaipentagon hexacontapentagon hexecontapentagon
66 hexacontakaihexagon hexacontahexagon hexecontahexagon
67 hexacontakaiheptagon hexacontaheptagon hexecontaheptagon
68 hexacontakaioctagon hexacontaoctagon hexecontaoctagon
69 hexacontakaienneagon hexacontaenneagon hexecontaenneagon
70 heptacontagon hebdomecontagon
71 heptacontakaihenagon heptacontahenagon hebdomecontahenagon
73 heptacontakaitrigon heptacontatrigon hebdomecontatrigon
74 heptacontakaitetragon heptacontatetragon hebdomecontatetragon
75 heptacontakaipentagon heptacontapentagon hebdomecontapentagon
76 heptacontakaihexagon heptacontahexagon hebdomecontahexagon
77 heptacontakaiheptagon heptacontaheptagon hebdomecontaheptagon
78 heptacontakaioctagon heptacontaoctagon hebdomecontaoctagon
79 heptacontakaienneagon heptacontaenneagon hebdomecontaenneagon
80 octacontagon ogdoecontagon
81 octacontakaihenagon octacontahenagon ogdoecontahenagon
83 octacontakaitrigon octacontatrigon ogdoecontatrigon
84 octacontakaitetragon octacontatetragon ogdoecontatetragon
85 octacontakaipentagon octacontapentagon ogdoecontapentagon
86 octacontakaihexagon octacontahexagon ogdoecontahexagon
87 octacontakaiheptagon octacontaheptagon ogdoecontaheptagon
88 octacontakaioctagon octacontaoctagon ogdoecontaoctagon
89 octacontakaienneagon octacontaenneagon ogdoecontaenneagon
90 enneacontagon enenecontagon
91 enneacontakaihenagon enneacontahenagon enenecontahenagon
93 enneacontakaitrigon enneacontatrigon enenecontatrigon
94 enneacontakaitetragon enneacontatetragon enenecontatetragon
95 enneacontakaipentagon enneacontapentagon enenecontapentagon
96 enneacontakaihexagon enneacontahexagon enenecontahexagon
97 enneacontakaiheptagon enneacontaheptagon enenecontaheptagon
98 enneacontakaioctagon enneacontaoctagon enenecontaoctagon
99 enneacontakaienneagon enneacontaenneagon enenecontaenneagon
100 hectogon hecatontagon hecatogon
120 hecatonicosagon dodecacontagon
200 dihectagon diacosigon
300 trihectagon triacosigon
400 tetrahectagon tetracosigon
500 pentahectagon pentacosigon
600 hexahectagon hexacosigon
700 heptahectagon heptacosigon
800 octahectagon octacosigon
900 enneahectagon enacosigon
1000 chiliagon
2000 dischiliagon dichiliagon
3000 trischiliagon trichiliagon
4000 tetrakischiliagon tetrachiliagon
5000 pentakischiliagon pentachiliagon
6000 hexakischiliagon hexachiliagon
7000 heptakischiliagon heptachiliagon
8000 octakischiliagon octachiliagon
9000 enneakischiliagon enneachilliagon
10000 myriagon
20000 dismyriagon dimyriagon
30000 trismyriagon trimyriagon
40000 tetrakismyriagon tetramyriagon
50000 pentakismyriagon pentamyriagon
60000 hexakismyriagon hexamyriagon
70000 heptakismyriagon heptamyriagon
80000 octakismyriagon octamyriagon
90000 enneakismyriagon enneamyriagon
100000 decakismyriagon decamyriagon
200000 icosakismyriagon icosamyriagon
300000 triacontakismyriagon tricontamyriagon
400000 tetracontakismyriagon tetracontamyriagon
500000 pentacontakismyriagon pentacontamyriagon
600000 hexacontakismyriagon hexacontamyriagon
700000 heptacontakismyriagon heptacontamyriagon
800000 octacontakismyriagon octacontamyriagon
900000 enneacontakismyriagon enneacontamyriagon
1000000 hecatontakismyriagon megagon
2000000 diacosakismyriagon dimegagon
3000000 triacosakismyriagon trimegagon
4000000 tetracosakismyriagon tetramegagon
5000000 pentacosakismyriagon pentamegagon
6000000 hexacosakismyriagon hexamegagon
7000000 heptacosakismyriagon heptamegagon
8000000 octacosakismyriagon octamegagon
9000000 enneacosakismyriagon enneamegagon
10000000 chiliakismyriagon decamegagon
20000000 dischiliakismyriagon icosamegagon
30000000 trischiliakismyriagon triacontamegagon
40000000 tetrakischiliakismyriagon tetracontamegagon
50000000 pentakischiliakismyriagon pentacontamegagon
60000000 hexakischiliakismyriagon hexacontamegagon
70000000 heptakischiliakismyriagon heptacontamegagon
80000000 octakischiliakismyriagon octacontamegagon
90000000 enneakischiliakismyriagon enneacontamegagon
100000000 myriakismyriagon hectamegagon
apeirogon