Somewhat uncertain, but likely derived from *dubos (in doubt, adj.), from Proto-Italic *du(i)fwos, from Proto-Indo-European *dwi- (two-) + *bʰuH- (to be), with the same latter element as in superbus, probus (less likely tribus), in this case parallel to Ancient Greek διφυής (diphuḗs, of two shapes or natures). Or less likely, directly from Proto-Indo-European *dubʰi- (on two sides).

For the relation to "two" cf. Ancient Greek δισσός (dissós, twofold; doubtful), δοιάζω (doiázō, to be in two minds) and German Zweifel (doubt).



dubius (feminine dubia, neuter dubium); first/second-declension adjective

  1. Moving in two directions alternately, vibrating to and fro, fluctuating, wavering.
  2. (figuratively) Vacillating in mind, uncertain; doubting, doubtful, dubious, irresolute, undetermined.
  3. (of a situation) Precarious, dangerous, critical, difficult, adverse, doubtful.
  4. (of weather) Changeable, uncertain.


First/second-declension adjective.

Number Singular Plural
Case / Gender Masculine Feminine Neuter Masculine Feminine Neuter
Nominative dubius dubia dubium dubiī dubiae dubia
Genitive dubiī dubiae dubiī dubiōrum dubiārum dubiōrum
Dative dubiō dubiō dubiīs
Accusative dubium dubiam dubium dubiōs dubiās dubia
Ablative dubiō dubiā dubiō dubiīs
Vocative dubie dubia dubium dubiī dubiae dubia


Derived termsEdit

Related termsEdit


  • English: dubious
  • Italian: dubbio
  • Portuguese: dúbio
  • Sicilian: dùbbitu


  • De Vaan, Michiel (2008), “dubius”, in Etymological Dictionary of Latin and the other Italic Languages (Leiden Indo-European Etymological Dictionary Series; 7), Leiden, Boston: Brill, →ISBN, page 180
  • Walde, Alois; Hofmann, Johann Baptist (1938), “dubius”, in Lateinisches etymologisches Wörterbuch (in German), volume 1, 3rd edition, Heidelberg: Carl Winter, page 375

Further readingEdit

  • dubius in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
  • dubius in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
  • dubius in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
  • dubius in Gaffiot, Félix (1934) Dictionnaire illustré Latin-Français, Hachette
  • Carl Meißner; Henry William Auden (1894) Latin Phrase-Book[1], London: Macmillan and Co.
    • a critical position; a hopeless state of affairs: res dubiae, perditae, afflictae
    • vague rumours reach us: dubii rumores afferuntur ad nos
    • to throw doubt upon a thing: in dubio ponere
    • to leave a thing undecided: aliquid in medio, in dubio relinquere (Cael. 20. 48)
    • without doubt, beyond all doubt: sine dubio (not sine ullo dubio)
    • (ambiguous) to throw doubt upon a thing: in dubium vocare
    • (ambiguous) to become doubtful: in dubium venire
    • (ambiguous) to leave a thing undecided: aliquid dubium, incertum relinquere