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Latin Grammar I, Lesson 20. The Fifth Declension of Nouns

To complete this lesson, complete the following tasks:

  • Study the Lesson for mastery.
  • Complete all assignment Memory Work.
  • Complete all lesson Assessments.


In lesson 03, we were introduced to the “accidents” of the parts of speech.  In that lesson, I said:  “In this lesson, we will learn a little about each of these accidents, and then we will study them in detail throughout the rest of the course.”  In this lesson, we continue our detailed study of the declensions of Latin nouns.

In lesson 03, we learned that the Declensions of nouns are five.

  • The First declension, whose genitive singular is ended with the diphthong –AE, as musa, musae.
  • The Second declension, whose genitive singular is ended with the letter –I , as dominus, domini.
  • The Third declension, whose genitive singular is ended with (the) syllable –IS , as sermo, sermonis.
  • The Fourth declension, whose genitive singular is ended with the syllable –US , as sensus, sensus.
  • The Fifth declension, whose genitive singular is ended with the letters E and I, as dies, diei.

In this lesson, we will study the forms of the Fifth Declension nouns. Alvarez teaches us:

1. Nomina declinationis quintae recto casu desinunt in -es, et hac ratione variantur.

Translation: Nouns of the fifth declension end in the regular (case) in -ES, and by this rule (see below) are varied.

Example Noun of the Fifth Declension

Latin nouns of the fifth declension have their nominative case ending in -ES.  We will study one example noun of the fifth declension: hic dies, diei (day)


The example noun of the fifth declension is hic dies.  The pronoun hic marks the gender as masculine, and the noun is declined as follows:


  • Nominative:  hic di-es, day
  • Genitive: di-ei, of day
  • Dative:  di-ei, to day
  • Accusative:  di-em, day
  • Vocative:  O di-es, O day
  • Ablative:  a di-e, from day


  • Nominative:  hi di-es, days
  • Genitive: di-erum of days
  • Dative:  di-ebus, to days
  • Accusative:  di-es, days
  • Vocative:  O di-es, O days
  • Ablative:  a di-ebus, from days

Important:  We see that the ending of the genitive singular form is -EI, which marks this declension. Note that this is  NOT the diphthong EI, but two separate vowels, E and I. 

Plural Cases Not Used

In lesson 20, Alvarez teaches the following:

2. Casus interrogandi, dandi sextusque multitudinis praeter rerum rebus, dierum diebus inusitati sunt.  Cicero non est ausus specierum aut speciebus dicere, non tamen negat posse Latine dici.

Translation: (The) Genitive, Dative and Ablative cases of (the) plural (number), except for rerum, rebus and dierum, diebus, are not used.  Cicero did not dare to say specierum or speciebus, not nevertheless does he deny (it) to be able to be said in Latin.

What we learn here is that the fifth declension nouns–except for res (thing) and dies (day)–do not make the Genitive, Dative or Ablative cases in the plural number.  He provides proof of this from the writings of Cicero, where he speaks of this directly.  Cicero writes (translation by Yonge):

“ In division, there are forms which the Greeks call ideai; our countrymen who treat of such subjects call them species. And it is not a bad name, though it is an inconvenient one if we want to use it in different cases. For even if it were Latin to use such words, I should not like to say “specierum” and “speciebus”. And we have often occasion to use these cases. But I have no such objection to saying “formarum” and “formis”; and as the meaning of each word is the same, I do not think that convenience of sound is wholly to be neglected.” (Topics, 7)

Nevertheless, Cicero grants that they may be used in Latin, but that he would not use them because they lack a “convenience of sound”, that is, they aren’t pleasant to say or hear. See the tutorial for more info.

Substantives and Adjectives

After learning the forms of the example nouns of the fourth declension, we must give attention to the declension of substantives with adjectives.   Adjective nouns have cases just like substantives, so when they are used together, they must always be written with the same gender, numbichaeler and case. Here are some examples to be declined:

  • hic dies laetissimus
  • haec species insignis
  • haec res familiaris
  • haec facies honesta et liberalis

First, let us consider hic dies, with an adjective of the second declension:


  • Nominative:  hic dies laetissimus most happy day
  • Genitive: diei laetissimi of (a) most happy day
  • Dative:  diei laetissimo to (a) most happy day
  • Accusative:  diem laetissimum most happy day
  • Vocative:  O dies laetissime O most happy day
  • Ablative:  a die laetissimo from (a) most happy day


  • Nominative:  hi dies laetissimi most happy days
  • Genitive: dieerum laetissimorum of most happy days
  • Dative:  diebus laetissimis to most happy days
  • Accusative:  dies laetissimos most happy days
  • Vocative:  O dies laetissimi O most happy days
  • Ablative:  a diebus laetissimis from most happy days

Now, let us consider the feminine fifth declension noun haec res with an adjective of the third declension.  Notice that, while the endings differ, the gender, number and case they signify remain the same:


  • Nominative: haec res familiaris (a) familiar thing
  • Genitive: rei familiaris of (a) familiar thing
  • Dative:  rei familiari to (a) familiar thing
  • Accusative:  rem familiarem (a) familiar thing
  • Vocative:  O res familiaris O familiar thing
  • Ablative:  a re familiari from (a) familiar thing


  • Nominative: hae rei familiares familiar things
  • Genitive: rerum familiarium of familiar things
  • Dative:  rebus familiaribus to familiar things
  • Accusative:  res familares familiar things
  • Vocative:  O res familiares O familiar things
  • Ablative:  a rebus familiaribus from familiar things

Remember, substantives and adjectives from different declensions may be joined, but they must agree in gender, number and case.  They may not look the same, but their characteristics must be the same.

Memory Work

To learn the declensions, you must relay on memorization.  Recite the questions and answers below until they are thoroughly memorized.  Rely on the lesson assessments to test your progress.

1. How many different terminations are found in the Nominative case of the Fifth Declension?
One: -es.

2. Decline the Fifth Declension masculine noun hic dies (day). (State the case name, the Latin form and the English.)
Singular: Nominative, hic dies, day; Genitive, diei, of day; Dative; diei, to day, Accusative, diem, day; Vocative, O dies, O day; Ablative, a die, from day. Plural: Nominative, dies, days; Genitive, dierum, of days; Dative, diebus, to days; Accusative, dies, days; Vocative, O dies, O days; Ablative, a diebus, from days.

In short: Dies, Diei, Diei, Diem, O Dies, a Die;  Dies, Dierum, Diebus, Dies, O Dies, a Diebus.

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