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manus, cornū: the fourth declension

Nouns in -us with a genitive in -ūs, and neuters in -ū.

LatinIntermediate Latin · The fourth and fifth declensionsAbout 3 min: 1 reading, 2 practiceUpdated

After this lesson you can
  • Recognise fourth-declension nouns from the genitive -ūs
  • Decline adventus and cornū
  • Remember that manus and domus are feminine
Latin Level 2: verbs and the other declensions: lesson 24 of 35
  1. Intermediate Latin · Verbs: the present system
  2. sum: I am, I was, I shall be 3 min
  3. The present of amō and moneō 4 min
  4. The imperfect: was doing 4 min
  5. The future: will do 3 min
  6. The dative with adjectives 3 min
  7. The present of regō and audiō 4 min
  8. The imperfect of regō and audiō, and verbs that take the dative 3 min
  9. The future of regō and audiō 3 min
  10. capiō, and giving orders 3 min
  11. Intermediate Latin · The passive voice
  12. The passive: being done to 3 min
  13. The passive of regō, audiō and capiō; passive infinitives 3 min
  14. Synopses, and the ablative of "from" 3 min
  15. Intermediate Latin · The perfect tenses
  16. fuī, fueram, fuerō: the perfect tenses of sum 3 min
  17. The perfect active: did, have done 5 min
  18. Had done, will have done: pluperfect and future perfect active 3 min
  19. amātus sum: the perfect passive 4 min
  20. Principal parts, prepositions, and yes-or-no questions 5 min
  21. possum, "I can", and the infinitive 3 min
  22. Intermediate Latin · Pronouns
  23. quī, quae, quod: who, which, that 4 min
  24. Intermediate Latin · The third declension
  25. rēx, rēgis: the third declension 4 min
  26. hostis, urbs, mare: i-stems 4 min
  27. vīs and iter; gender in the third declension 4 min
  28. omnis, ācer, pār: third-declension adjectives 3 min
  29. Intermediate Latin · The fourth and fifth declensions
  30. manus, cornū: the fourth declension 3 min
  31. Rōmae, domī, Athēnīs: place and the locative 4 min
  32. diēs, rēs: the fifth declension and the ablative of time 3 min
  33. Intermediate Latin · Pronouns
  34. ego, tū, sē: personal and reflexive pronouns 4 min
  35. ipse, "himself", and īdem, "the same" 3 min
  36. hic, iste, ille: this and that 4 min
  37. aliquis, quīdam, quisque: someone, a certain, each 3 min
  38. Intermediate Latin · Comparison
  39. clārior, clārissimus: comparing adjectives 4 min
  40. melior, optimus: irregular comparison, plūs, and "by how much" 3 min
  41. clārē, fortiter: adverbs and their comparison 4 min
  42. Intermediate Latin · Numerals
  43. ūnus, duo, trēs: numerals, "of" the whole, and "for how long" 5 min
  44. Intermediate Latin · Deponent verbs
  45. hortor, sequor: deponent verbs 3 min

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Pairs with D'Ooge, Latin for Beginners (Ginn, 1909), Lesson XLVI ("The Fourth or U-Declension"), §§ 259–260

What it is

The fourth declension has masculine nouns in -us and neuters in -ū. The genitive singular ends in -ūs, with a long ū, which is how you tell exercitus, exercitūs (army) from a second-declension word like servus, servī.

Caseadventus, m., arrivalcornū, n., horn, wing
Nom.adventuscornū
Gen.adventūscornūs
Dat.adventuīcornū
Acc.adventumcornū
Abl.adventūcornū
Nom. pl.adventūscornua
Gen. pl.adventuumcornuum
Dat./Abl. pl.adventibuscornibus

(Accusative plural: adventūs, cornua.) A few are feminine: manus (hand; band of men) and domus (house, home).

Quick check

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  1. Which noun is fourth declension?

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    exercitus, exercitūs. Genitive -ūs marks the fourth declension.

Why it matters

Army words are fourth declension: exercitus (army), equitātus (cavalry), impetus (attack), and cornū for the wing of an army. So are manus and domus. You'll meet them constantly in Caesar.

Worked example

  • Exercitus adventum lēgātī videt. → The army sees the lieutenant's arrival.
  • Impetus equitātūs erat ācer. → The cavalry's attack was fierce.
  • Ā dextrō cornū → on the right wing.

Common mistake

Reading -us as second declension. In manus, exercitus and impetus the genitive singular is -ūs, the nominative and accusative plural are -ūs, and the dative plural is -ibus: exercitibus, not wrong: exercitīs.

Key terms

exercitus, -ūs, m.
army
equitātus, -ūs, m.
cavalry
impetus, -ūs, m.
attack
adventus, -ūs, m.
arrival
manus, -ūs, f.
hand; band of men
cornū, -ūs, n.
horn; wing of an army

Practise the key terms

Tap a card to turn it over. 6 cards.

FrontBack
exercitus, -ūs, m.army
equitātus, -ūs, m.cavalry
impetus, -ūs, m.attack
adventus, -ūs, m.arrival
manus, -ūs, f.hand; band of men
cornū, -ūs, n.horn; wing of an army

Practice

Recognition drill

Pick the right answer, as fast as you can.

All pairs

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FrontBack
genitive singular of exercitusexercitūs
accusative singular of manusmanum
ablative singular of impetusimpetū
nominative plural of cornūcornua
genitive plural of exercitusexercituum
dative plural of manusmanibus

Quick quiz

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  1. Gender of manus

    Show answer

    feminine. manus and domus are feminine.

  2. Dative plural of exercitus

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    exercitibus. Fourth declension: -ibus.

Practise speaking

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You are a patient Latin tutor. Use the classical pronunciation only, never the Church one: c is always k, g is always hard, v sounds like w, ae like the ai in aisle, and long vowels are held longer. Speak slowly. Use only these Latin words: exercitus, equitātus, impetus, adventus, manus, cornū, magnus, videt. Give me a noun and a case in English (for example 'of the army', 'the attacks, accusative' or 'with a hand'), and I will say the Latin form aloud. Do 10 forms. After each answer, tell me what kind of mistake I made, if any, and let me try again, then tell me one thing to improve. Keep every reply under 2 sentences. If I need a name or a town, I will make one up. Speak English except for the Latin itself.

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Good to know. AI feedback on pronunciation is hit and miss, so check yourself against native recordings. This course teaches the classical pronunciation (see lesson 1); AI voices may mix it with the Church (Italian-style) one, so ask for classical and check against lesson 1. Don't share personal details: use a made-up name and town.

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In short

  • Genitive singular -ūs marks the fourth declension.
  • Masc. -us, -ūs, -uī, -um, -ū; -ūs, -uum, -ibus, -ūs, -ibus.
  • Neuter -ū: cornū, cornua.
  • manus and domus are feminine.

Mastery check

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Check yourself

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  1. Give the accusative singular of adventus.

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    adventum.

  2. How can you tell exercitus is fourth declension?

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    Its genitive is exercitūs, in -ūs.

  3. Translate Impetus equitātūs erat magnus.

    Show answer

    The attack of the cavalry was great.

Further reading

  • D'Ooge, Latin for Beginners, Lesson XLVI, §§ 259–260. Public domain; Project Gutenberg.