Post-classically attested, thus perhaps a back-formation from quadrō. See also quattuor, quārtus.

• (Classical Latin) IPA^(key): [ˈkʷa.drʊs]
• (modern Italianate Ecclesiastical) IPA^(key): [ˈkʷaː.drus]

quadrus (feminine quadra, neuter quadrum); first/second-declension adjective

1. square

First/second-declension adjective.

• ^?quadra
• ^?quadrō
• quadrum

• Catalan: caire
• Italian: squadra, quadro
• Old French: esquarre
  • French: équerre
  • Norman: êtchèrre
  • → English: square
    • → Latvian: skvērs
    • → Polish: skwer
    • → Thai: สแควร์ (sà-kwɛɛ)
    • → Welsh: sgwâr
• Venetan: quadro
• West Iberian
  • Portuguese: quadro
  • Spanish: cuadro
• ⇒ Vulgar Latin: *quadrellus
  • Italo-Dalmatian
    • Dalmatian: cadrial
    • Italian: quadrello
  • Old French: quarel
    • French: carreau
    • → English: quarrel
  • Venetan: quarel, quareło, cuadrèl, cuarèlo, cuarèl
    • → Cimbrian: korèll
  • West Iberian
    • Portuguese: quadrelo
    • Spanish: cuadrillo
• → Catalan: quadre

• “quadrus”, in Charlton T. Lewis and Charles Short (1879), A Latin Dictionary, Oxford: Clarendon Press
• "quadrus", in Charles du Fresne du Cange, Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
• “quadrus”, in Gaffiot, Félix (1934), Dictionnaire illustré latin-français, Hachette.
• Sihler, Andrew L. (1995), New Comparative Grammar of Greek and Latin, Oxford, New York: Oxford University Press, →ISBN
• De Vaan, Michiel (2008), “quattuor”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, page 505