Third Declension
Genitive Singular Ends in -IS

By definition, the third declension has a genitive singular form ending in -is. Your textbook has examples such as this:

Pastor, pastoris (masculine)

Case Singular Plural
Nominative pastor pastōrēs
Genitive pastōris pastōrum
Dative pastōrī pastōribus
Accusative pastōrem pastōrēs
Ablative pastōre pastōribus

N.B. For nouns of the third declension, masculine and feminine follow the same pattern.

Here is an English equivalent of the chart above.

Case Singular Plural
Nominative shepherd shepherds
Genitive shepherd's shepherds'
Dative to/for the shepherd to/for the shepherds
Accusative shepherd(object) shepherds (object)
Ablative from/with/in/by the shepherd from/with/in/by the shepherds

N.B. Latin is an inflected language. The form of a noun determines how it is being used. A subject, an object, a possessive -- each has its own particular form.

Things you must know about NOUNS of the THIRD DECLENSION:

  • Genitive Singular = -is
  • They follow the same pattern for masculine and feminine
  • The pattern for neuter nouns (see below) differs from the masculine and feminine only in the nominative plural and in the accusative singular and plural
  • The nominative singular form is unpredictable, represented as -- in the chart below
  • The accusative neuter singular (--) repeats the nominative neuter form.

Subject -- -ēs -- -a
"of" -is -um -is -um
"to" or "for" -ibus -ibus
Object -em -ēs -- -a
"from", "with", "in", "on", "by" -e -ibus -e -ibus

Third Declension I-Stem Nouns

Many nouns of the third declension retain an -i- in the stem of the plural genitive form (-ium). Most neuter nouns also retain an -i- in the stem of the plural nominative and accusative (-ia) and in the ablative singular ().

Ovis, ovis (f) (i-stem) Sheep

Case Singular Plural
Nominative ovis ovēs
Genitive ovis ovium
Dative ovī ovibus
Accusative ovem ovēs
Ablative ove ovibus

Mare, maris (n) (i-stem) sea

Case Singular Plural
Nominative mare maria
Genitive maris marium
Dative marī maribus
Accusative mare maria
Ablative marī maribus

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