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From Proto-Italic *lakus, from Proto-Indo-European *lókus (lake, pool). Cognate with Ancient Greek λάκκος (lákkos, cistern, tank, pit) and Old English lagu (sea, ocean, flood). More at lay.



lacus m (genitive lacūs); fourth declension

  1. a lake, pond, basin; reservoir
  2. a tank, tub, vat, sink


Fourth-declension noun (dative/ablative plural in -ubus).

Case Singular Plural
Nominative lacus lacūs
Genitive lacūs lacuum
Dative lacuī lacubus
Accusative lacum lacūs
Ablative lacū lacubus
Vocative lacus lacūs

Derived termsEdit



  • lacus in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
  • lacus in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
  • lacus in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition, 1883–1887)
  • lacus in Gaffiot, Félix (1934) Dictionnaire Illustré Latin-Français, Hachette
  • lacus in Harry Thurston Peck, editor (1898) Harper's Dictionary of Classical Antiquities, New York: Harper & Brothers
  • lacus in William Smith et al., editor (1890) A Dictionary of Greek and Roman Antiquities, London: William Wayte. G. E. Marindin