Lesson 13: 4th and 5th Declension Nouns

Full paradigms for 4th-declension masculine and neuter nouns and 5th-declension nouns, with key vocabulary and the special behavior of domus.

latinnovicelesson

Overview

The 4th and 5th declensions are the smallest declension groups in Latin, but they include some extremely common words — manus (hand), domus (house), exercitus (army), rēs (thing), and diēs (day). Learning these paradigms gives you the final pieces of the Latin noun system.

1. Fourth Declension — Masculine/Feminine

The 4th declension is identified by -ūs in the genitive singular. Most nouns are masculine; a few are feminine (manus, domus).

Model: manus, manūs f. — hand

Case Singular Plural
Nom. manus manūs
Gen. manūs manuum
Dat. manuī manibus
Acc. manum manūs
Abl. manū manibus
Voc. manus manūs

Watch out: Nominative singular and accusative plural both end in -ūs. Distinguish by context.

2. Fourth Declension — Neuter

Neuter 4th-declension nouns end in -ū in the nominative singular.

Model: cornū, cornūs n. — horn, wing (of an army)

Case Singular Plural
Nom./Voc./Acc. cornū cornua
Gen. cornūs cornuum
Dat. cornū cornibus
Abl. cornū cornibus

3. Notable 4th Declension Nouns

Latin Gen. Gender English
manus, manūs manūs f. hand; band of men
domus, domūs domūs f. house, home
senātus, senātūs senātūs m. senate
exercitus, exercitūs exercitūs m. army
lacus, lacūs lacūs m. lake
portus, portūs portūs m. harbor, port
gradus, gradūs gradūs m. step, degree
currus, currūs currūs m. chariot
vultus, vultūs vultūs m. face, expression
impetus, impetūs impetūs m. attack, impulse

4. domus — The Irregular House

Domus mixes 4th and 2nd declension forms. Certain forms come from the 2nd declension (domī, domō, domum), especially in fixed expressions:

Case Singular Plural
Nom. domus domūs / domī
Gen. domūs / domī domuum / domōrum
Dat. domuī / domō domibus
Acc. domum domōs / domūs
Abl. domō / domū domibus

Key idiomatic forms:

  • domī — at home (locative; not a normal case, fossilized form)
  • domum — homeward, to home (accusative of motion without a preposition)
  • domō — from home (ablative of separation without a preposition)

These three (domī, domum, domō) are among the most common Latin idioms. Memorize them as fixed expressions.

5. Fifth Declension

The 5th declension is identified by -ēī in the genitive singular. Nearly all nouns are feminine. Diēs (day) is mostly masculine but becomes feminine when referring to a specific/appointed day.

Model A: rēs, reī f. — thing, matter, affair, situation

Case Singular Plural
Nom. rēs rēs
Gen. reī rērum
Dat. reī rēbus
Acc. rem rēs
Abl. rē rēbus

Model B: diēs, diēī m./f. — day

Case Singular Plural
Nom. diēs diēs
Gen. diēī diērum
Dat. diēī diēbus
Acc. diem diēs
Abl. diē diēbus

6. Notable 5th Declension Nouns

Latin Gen. Gender English
rēs, reī reī f. thing, matter, affair
diēs, diēī diēī m./f. day
spēs, speī speī f. hope
fidēs, fideī fideī f. faith, trust, loyalty
aciēs, aciēī aciēī f. line of battle, sharp edge
faciēs, faciēī faciēī f. face, appearance
speciēs, speciēī speciēī f. appearance, kind, species

Important: Most 5th-declension nouns are rare in the plural or lack certain plural forms. Rēs and diēs are the only ones fully common in the plural.

7. Common Phrases with rēs

Rēs is one of Latin's most versatile words. Key compounds and phrases:

Latin English
rēs pūblica the state, republic (the public affair)
rēs gestae achievements, deeds
rēs mīlitāris military affairs/science
rē vērā in truth, actually
ob eam rem for that reason
omnes rēs all things, everything

Example Sentences

  1. Exercitus Rōmānus ad portum marched. — The Roman army marched to the harbor.
  2. Cornua exercitūs ā duce extenduntur. — The wings of the army are extended by the commander.
  3. Marcus domum festīnat. — Marcus hurries home.
  4. Puella domī manet. — The girl stays at home.
  5. Spēs nostra magna est. — Our hope is great.
  6. Fidēs Rōmānōrum clāra erat. — The faith/loyalty of the Romans was famous.
  7. Multōs diēs in villā mānsimus. — We stayed at the villa for many days.
  8. Rēs pūblica in perīculō est. — The republic is in danger.
  9. Manus mīlitum oppidum cēpit. — A band of soldiers captured the town.
  10. Hōc diē hostes profectī sunt. — On this day the enemy set out.
  11. Per gradūs ascendēbant. — They were climbing by steps.
  12. Impetus hostium repulsus est. — The attack of the enemy was repelled.

Practice

A. Decline fully (sg. and pl.):

  1. portus, portūs m.
  2. spēs, speī f.

B. Identify case and number:

  1. exercituum
  2. reī
  3. domō
  4. manibus
  5. diēbus

C. Translate:

  1. The senate meets at home. (Use convenit = meets, assembles.)
  2. The hope of the soldiers was great.
  3. On many days the army attacked the harbor.