triangulum

Forms

triangulum n (genitive triangulī); second declension^[1]

Etymology

It is from Latin triangulus (“three-cornered, triangular”), the neuter of the adjective used as a noun.^[2][3] The adjective is formed from tri- (“three”) and angulus (“corner, angle”).^[2][4][3]

Earliest recorded meaning

It is found from Cicero on,^[5] who uses the noun for a triangle in De natura deorum.^[4][6]

Semantic evolution

The adjective triangulus described three-cornered things: a shape of skin in Celsus, a field in Columella and the outline of Sicily in Pliny the Elder.^[4][7] In astronomy the neuter plural named stars standing a third of the zodiac apart, beside quadrata for those a quarter apart.^[2][7] The land surveyors also used a masculine noun triangulus for the figure.^[7][6]

Medieval geometry kept the noun and the adjective, as in Adelard's Elements.^[8] It passed into French as triangle, and German Triangel and Middle High German drīangel go back to it.^[1][5]

Timeline

• 81–43 BC – Cicero uses the noun for a triangle and the adjective of stars in a trine aspect.^[2][4][5]
• 14–37 AD – Celsus uses the adjective of a three-cornered shape.^[4][7][5]
• 1st century AD – Columella speaks of a triangular field.^[4][5]
• 23/24–79 AD – Pliny the Elder uses both the noun and the adjective.^[4][6][5]
• c. 35–95/96 AD – Quintilian notes that squares enclose more space than triangles: quadrata amplius spatium complectuntur triangulis.^[4][5]
• late 14th century – English takes it over as triangle, partly through French.^[3]

Meanings

Noun

1. A triangle.^[2][4][7]
2. (astronomy, plural) Stars standing in a trine aspect, a third of the zodiac apart.^[2][7]

Word family

• triangulāris

Related words

• angulus
• English triangle

References

1. ^ a b c d Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f Glare, P. G. W., ed. (2012), Oxford Latin Dictionary, 2nd ed., Oxford: Oxford University Press
3. ^ a b c Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c d e f g h i Lewis, Charlton T.; Short, Charles (1879), A Latin Dictionary, Oxford: Clarendon Press
5. ^ a b c d e f g Köbler, Gerhard (2010), Lateinisches Abkunfts- und Wirkungswörterbuch für Altertum und Mittelalter, online ed., koeblergerhard.de
6. ^ a b c Gaffiot, Félix (2016), Dictionnaire latin-français, new ed. by Gérard Gréco et al. (Gaffiot 2016), online ed.
7. ^ a b c d e f Georges, Karl Ernst (1913–1918), Ausführliches lateinisch-deutsches Handwörterbuch, 8th ed., ed. Heinrich Georges, Hannover; Leipzig: Hahn
8. ^ Latham, R. E., D. R. Howlett, R. K. Ashdowne, et al. (1975–2013), Dictionary of Medieval Latin from British Sources, London: British Academy / Oxford University Press