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Latin Grammar I, Lesson 13. The Third Declension of Nouns

To complete this lesson, complete the following tasks:

  1.  Study the Lesson for mastery.
  2. Complete all assignment Memory Work.
  3. 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 begin our detailed study of the declensions of Latin nouns.

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

  • The First declension, whose genitive singular is ended with the diphthong -AE, as musamusae.
  • The Second declension, whose genitive singular is ended with the letter -I , as dominusdomini.
  • The Third declension, whose genitive singular is ended with (the) syllable -IS , as sermosermonis.
  • The Fourth declension, whose genitive singular is ended with the syllable -US , as sensussensus.
  • The Fifth declension, whose genitive singular is ended with the letters E and I, as diesdiei.

In this lesson, we will study the forms of the Third Declension nouns.

Example Nouns of the Third Declension

In the nominative case, third declension nouns may end in as many as 11 different letters:  -a, -e, -o, -c, -d, -l, -n, -r, -s, -t, or -x.  Though there are many situations among third declension nouns, one thing will always be the same: the genitive singular ends with -IS.

In comparison to the nominative case, the genitive case of a third declension noun is either:

of an equal number of syllables, as civ•is, civ•is (citizen); or,
longer by one syllable, as ser•mo, ser•mon•is (speech); or,
longer by two syllables, as i•ter, i•ti•ner•is (journey).

The three example nouns we will study for the third declension are:

hic sermo, sermonis (speech)
hoc tempus, temporis (time)
hic & haec parens, parentis (parent)


The first example noun of the this declension is hic sermo.  The pronoun hic marks the gender as masculine, and the noun is declined as follows:


Nominative:  hic sermo, (the) speech
Genitive: sermon-is of (the) speech
Dative:  sermon-i, to (the) speech
Accusative:  sermon-em, (the) speech
Vocative:  O sermo, O speech
Ablative:  a sermon-e, from (the) speech


Nominative:  hi sermon-es, (the) speeches
Genitive: sermon-um of (the) speeches
Dative:  sermon-ibus, to (the) speeches
Accusative:  sermon-es, (the) speeches
Vocative:  O sermon-es, O speeches
Ablative:  a sermon-ibus, from (the) speeches

We see that the ending of the genitive singular form is -IS, which marks this declension.  Note, most significantly, the endings -IBUS in the dative and ablative plural.  These are very commonly seen in Latin reading, and now you know their meaning.


The second example noun of the third declension is the noun hoc tempus.  The pronoun hoc marks this as a neuter noun, and it is declined as follows:


Nominative:  hoc tempus, (the) time
Genitive: tempor-is of (the) speech
Dative:  tempor-i, to (the) speech
Accusative:  tempus, (the) speech
Vocative:  O tempus, O speech
Ablative:  a tempor-e, from (the) speech


Nominative:  haec tempor-a, (the) times
Genitive: tempor-um of (the) times
Dative:  tempor-ibus, to (the) times
Accusative:  tempor-a, (the) times
Vocative:  O tempor-a, O times
Ablative:  a tempor-ibus, from (the) times

Note here that seeing a word ending in -US in Latin does not make it a second declension noun like dominus.  This is why it is important to remember that declensions are identified by the genitive singular ending.


The third example noun of the third declension is the noun hic, haec parens.  The pronouns hic and haec marks this as a noun whose gender is “common of two”, because the same noun can be used to name a masculine or feminine object. It is declined as follows:


Nominative:  hic, haec parens, (a) parent
Genitive: parent-is of (a) parent
Dative:  parent-i, to (a) parent
Accusative:  parens, (a) parent
Vocative:  O parens, O parent
Ablative:  a parent-e, from (a) parent


Nominative:  haec parent-es, parents
Genitive: parent-um of parents
Dative:  parent-ibus, to parents
Accusative:  parent-es, parents
Vocative:  O parent-es O parents
Ablative:  a parent-ibus, from parents

Other examples of the common of two nouns of the third declension are: hic et haec civis (citizen),  hic et haec hostis (enemy).

Substantives and Adjectives

After learning the forms of the example nouns of the second 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, number and case. Here are some examples to be declined:

hic sermo elegans
hic panis quotidianus
haec virtus admiranda
haec oratio elegantior
hoc munus pretiosum
hoc flumen velox
hoc nomen celebre
hoc corpus perspicuum

First, let us consider hic sermo, with an adjective of the third declension:


Nominative:  hic sermo elegans, (an) elegant speech
Genitive: sermon-is elegant-is of (an) elegants peech
Dative:  sermon-i elegant-i, to (an) elegant speech
Accusative:  sermon-em elegant-em, (an) elegant speech
Vocative:  O sermo elegans, O elegant speech
Ablative:  a sermon-e elegant-e, from (an) elegant speech


Nominative:  hi sermon-es elegantes, elegant speeches
Genitive: sermon-um elegant-um of elegant speeches
Dative:  sermon-ibus elegeant-ibus, to elegant speeches
Accusative:  sermon-es elegant-es, elegant speeches
Vocative:  O sermon-es elegant-es, O elegant speeches
Ablative:  a sermon-ibus elegantibus, from elegant speeches

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


Nominative:  haec virtus admirand-a, (an) admirable virtue
Genitive: virtut-is admirand-ae of (an) admirable virtue
Dative:  virtut-i admirand-ae, to (an) admirable virtue
Accusative:  virtut-em admirand-am, (an) admirable virtue
Vocative:  O virtus admirand-a, O admirable virtue
Ablative:  a virtut-e admirand-a, from (an) admirable virtue


Nominative:  hi virtut-es admirand-ae, admirable virtues
Genitive: virtut-um admirand-arum of admirable virtues
Dative:  virtut-ibus admirand-is, to admirable virtues
Accusative:  virtut-es admirand-as, admirable virtues
Vocative:  O virtut-es admirand-ae, O admirable virtues
Ablative:  a virtut-ibus admirand-is, from admirable virtues

Now, let us consider the third declension neuter noun hoc nomen (declined like hoc tempus):


Nominative:  hoc nomen celebre, (the) famous name
Genitive: nomin-is celebr-is of (the) famous name
Dative:  nomin-i celebr-i, to (the) famous name
Accusative:  nomen celebre, (the) famous name
Vocative:  O nomen celebre, O famous name
Ablative:  a nomin-e celebr-i, from (the) famous name


Nominative:  haec nomin-a celebr-ia, (the) famous names
Genitive: nomin-um celebr-ium of (the) famous names
Dative:  nomin-ibus celebr-ibus, to (the) famous names
Accusative:  nomin-a celebr-ia, (the) famous names
Vocative:  O nomin-a celebr-ia, O famous names
Ablative:  a nomin-ibus celebr-ibus, from (the) famous names

Note that the endings of the third declension adjective celebre differ in that they add an -I in some endings.

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 Third Declension?
Eleven: -a, -e, -o | -c, -d, -l | -n, -r, -s, -t, -x.

2. Decline the Third Declension masculine noun hic Sermo. (State the case name, the Latin form and the English.)
Singular: Nominative, hic Sermo, a speech; Genitive, Sermonis, of a speech; Dative; Sermoni, to a speech, Accusative, Sermonem, a speech; Vocative, O Sermo, O speech; Ablative, a Sermone, from a speech. Plural: Nominative, Sermones, speeches; Genitive, Sermonum, of speeches; Dative, Sermonibus, to speeches; Accusative, Sermones, speeches; Vocative, O Sermones, O speeches; Ablative, a Sermonibus, from speeches.

In short: Sermo, Sermonis, Sermoni, Sermonem, O Sermo, a Sermone;  Sermones, Sermonum, Sermonibus, Sermones, O Sermones, a Sermonibus.

3. Decline the Third Declension neuter noun hoc Tempus (time). (State the case name, the Latin form and the English.)
Singular: Nominative, hoc Tempus, time; Genitive, Temporis, of time; Dative, Tempori, to time; Accusative, Tempus, time; Vocative, O Tempus, O time; Ablative, a Tempore, from time. Plural: Nominative, Tempora, times; Genitive, Temporum, of times; Dative, Temporibus, to times; Accusative, Tempora, times; Vocative, O Tempora, O times; Ablative, a Temporibus, from times.

In short: Tempus, Temporis, Tempori, Tempus, O Tempus, a Tempore; Tempora, Temporum, Temporibus, Tempora, O Tempora, a Temporibus.

4. What special rule applies to Neuter nouns of the Third Declension?
Neuter nouns of the Third Declension have the Accusative and Vocative the same as the Nominative in each Number.

5. Decline the Third Declension common-of-two noun hic et haec Parens (parent). (State the case name, the Latin form and the English.)
Singular: Nominative, hic et haec Parens, parent; Genitive, Parentis, of a parent; Dative, Parenti, to a parent; Accusative, Parentem, a parent; Vocative, O Parens, O parent; Ablative, a Parente, from a parent. Plural: Nominative, Parentes, parents; Genitive, Parentum, of parents; Dative, Parentibus, to parents; Accusative, Parentes, parents; Vocative, O Parentes, O parents; Ablative, a Parentibus, from parents.

In short: Parens, Parentis, Parenti | Parentem, O Parens, a Parente | Parentes, Parentum, Parentibus | Parentes, O Parentes, a Parentibus.


Lesson 13 Exam