πεντάγωνος

Forms

πεντάγωνος (pentágōnos) m or f (neuter πεντάγωνον); second declension^[1]

Etymology

It is a compound from Ancient Greek πέντε (pénte, “five”) + γωνία (gōnía, “angle, corner”),^[2][3][4][1] made like ἑξάγωνος (hexágōnos, “hexagonal”).^[5] Etymonline traces πέντε (pénte) to Proto-Indo-European *penkʷe- (“five”) and γωνία (gōnía) to *ǵenu- (“knee; angle”).^[6]

Earliest recorded meaning

It is first found in a fragment of Aristotle, meaning “pentagonal”.^[7]

Semantic evolution

It is a word of the mathematicians, and its neuter, used as a noun, is the geometers' pentagon: Euclid and Archimedes use it,^[8][1] and later Heron, Plutarch and Galen.^[8][7] Nicomachus speaks of pentagonal numbers and pentagonal bases.^[7]

Through French pentagone or Late Latin pentagonum the noun reached English as pentagon in the 1560s; the US military headquarters, completed in 1942, was named the Pentagon for its shape.^[6] Modern Greek keeps πεντάγωνος (pentágonos) as a learned word, and its neuter also names that building, a sense taken from English.^[9][10]

Timeline

• 4th century BC – Aristotle uses it for “pentagonal”.^[7][11]
• 3rd century BC – Euclid and Archimedes use the neuter for the pentagon.^[8][11]
• 1st–2nd century AD – Nicomachus writes of pentagonal numbers, and Plutarch uses the noun.^[7][11]
• 2nd century AD – Galen uses the noun.^[7][11]
• 1560s – English takes pentagon from it through French or Late Latin.^[6]
• Modern Greek – The learned πεντάγωνος (pentágonos) means “pentagonal”, and its neuter also names the Pentagon.^[9]

Meanings

Adjective

1. Pentagonal, having five angles.^[7][1][12]

Noun

1. (geometry, in the neuter) A pentagon.^[7][1][3]

Word family

• πενταγωνικός (pentagōnikós)

Related words

• πέντε (pénte)
• γωνία (gōnía)
• ἑξάγωνος (hexágōnos)
• English pentagon

References

1. ^ a b c d e f g h Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ Bailly, Anatole (2020), Dictionnaire grec-français, Bailly 2020 Hugo Chávez ed., ed. Gérard Gréco et al.
3. ^ a b Malhadas, Daisi; Dezotti, Maria Celeste C.; Neves, Maria Helena de Moura, eds. (2006–2010), Dicionário Grego-Português, São Paulo: Ateliê; digital ed. 3 (2022), UNESP Araraquara
4. ^ Köbler, Gerhard, Griechisch-deutsches Wörterbuch, online ed., https://www.koeblergerhard.de
5. ^ Πάπυρος–Larousse–Britannica, Μέγα Λεξικό της Ελληνικής Γλώσσας, Athens: Πάπυρος
6. ^ a b c Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
7. ^ a b c d e f g h Liddell, Henry George; Scott, Robert; Jones, Henry Stuart (1940), A Greek-English Lexicon, 9th ed., Oxford: Clarendon Press
8. ^ a b c Keersmaekers, Alek (2021–2025), GLAUx: The Greek Language Automated corpus, https://github.com/alekkeersmaekers/glaux
9. ^ a b Ινστιτούτο Νεοελληνικών Σπουδών (Ίδρυμα Μανόλη Τριανταφυλλίδη) (1998), Λεξικό της κοινής νεοελληνικής, Thessaloniki: Aristotle University of Thessaloniki
10. ^ Ακαδημία Αθηνών (2014), Χρηστικό Λεξικό της Νεοελληνικής Γλώσσας, Athens: Academy of Athens
11. ^ a b c d Rodríguez Adrados, Francisco, et al., eds. (1980–), Diccionario Griego-Español, Madrid: CSIC, http://dge.cchs.csic.es/xdge
12. ^ Korinthios, J. (2025), Grande Dizionario Greco Classico: Greco–Italiano, digital ed., Milan: Hoepli