Why does "Hominem unius libri timeo" use comparativus unius instead of positivus unum? Does it mean "I fear a man of one book (more)"? Or does that unius belong to hominem because it is accusativus+comparativus?

1 Answer 1


It looks like a comparative (cf. facilius, melius, and many others) but it is in fact a genitive. Thus unius libri is "of one book".

The word unus has an unusual declension:

  • nom: unus, una, unum
  • acc: unum, unam, unum
  • gen: unius
  • dat: uni
  • abl: uno, una, uno

The same genitive in -ius is used by a couple of pronouns.

There is no comparative form of unus in Latin, nor do I know what "onner" should mean.

  • Ah ok looks like the online dictionary is wrong, I checked somewhere else, most probably they generated the declinations. thanks!
    – oguzalb
    Sep 4, 2020 at 15:10
  • 2
    just to add the other eight that share the same irregularity: alius, alter, ullus, nullus, uter, neuter, solus, totus.
    – d_e
    Sep 4, 2020 at 15:14
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    @oguzalb I recommend Wiktionary (gets it right) or Collatinus (also gets it right but cannot be linked). Note that the pronunciation is different, by the way: the comparative has a short i and is stressed on the third to last syllable. Sep 4, 2020 at 15:47
  • 3
    @d_e: In addition, is, ille, iste, hic, and qui also have genitives on -ius.
    – Cerberus
    Sep 4, 2020 at 16:19

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