From Proto-Indo-European *h₂erk-. Cognates include Latin arca (chest, box), arceō (I defend), arcānus (hidden, secret), arcera (kind of wagon), Old Armenian արգել (argel, obstacle) and Ancient Greek ἀρκέω (arkéō).



arx f (genitive arcis); third declension

  1. citadel, stronghold, fortress
    • Vergil, Aeneid, 2.56:
      ... Trōiaque, nunc stārēs, Priamīque arx alta, manērēs.
      ... and Troy, you would now be standing, and Priam's mighty citadel still endure.
  2. height, summit, hilltop; the Capitoline hill
  3. defense, refuge
  4. (figuratively) bulwark


Third-declension noun (i-stem).

Case Singular Plural
Nominative arx arcēs
Genitive arcis arcium
Dative arcī arcibus
Accusative arcem arcēs
Ablative arce arcibus
Vocative arx arcēs


  • arx in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
  • arx in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
  • arx in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition, 1883–1887)
  • arx in Gaffiot, Félix (1934) Dictionnaire illustré Latin-Français, Hachette
  • arx in Harry Thurston Peck, editor (1898) Harper's Dictionary of Classical Antiquities, New York: Harper & Brothers
  • arx in Samuel Ball Platner (1929) , Thomas Ashby, editor, A Topographical Dictionary of Ancient Rome, London: Oxford University Press
  • arx in William Smith et al., editor (1890) A Dictionary of Greek and Roman Antiquities, London: William Wayte. G. E. Marindin