Lesson 7 – Third declension nouns and adjectives

Third declension nouns

You can identify third declension nouns by their genitive singular ending ‘-is’.

You cannot identify third declension nouns in the nominative because they

  • have various forms and spelling
  • have endings that do not reveal their gender
  • can be masculine, feminine or neuter

To decline a third declension noun:

  • find the genitive singular, which will end ‘-is’
  • remove the ‘-is’, leaving you with the stem
  • add the endings shown below

Endings for Masculine and Feminine nouns

Case Singular Plural
Nominative various -es
Vocative same as nominative -es
Accusative -em -es
Genitive -is -um
Dative -i -ibus
Ablative -e -ibus

Look at our example of rex, regis (m.) king

Case Singular Plural
Nominative rex reges
Vocative rex reges
Accusative regem reges
Genitive regis regum
Dative regi regibus
Ablative rege regibus

Endings for Neuter nouns

Case Singular Plural
Nominative various -a
Vocative same as nominative -a
Accusative same as nominative -a
Genitive -is -um
Dative -i -ibus
Ablative -e -ibus

The genitive, dative and ablative endings are the same as for rex.

Handy hints

Remember, nominative and accusative cases of neuter nouns are always the same. The plural always ends in ‘a’.

Look at our example of jus, juris (n.) law, right

Case Singular Plural
Nominative jus jura
Vocative jus jura
Accusative jus jura
Genitive juris jurum
Dative juri juribus
Ablative jure juribus

Common third declension nouns:

abbas, abbatis (m.) abbot
etas, etatis (f.) age
executor, executoris (m.) executor
heres, heredis (m., f.) heir
homo, hominis (m.) man
miles, militis (m.) knight
pater , patris (m.) father
uxor , uxoris (f.) wife

You need to know the genitive case of a third declension noun, in order to decline it.

Therefore, both the nominative and genitive forms are provided in full in this series of lessons.

curia domini Regis the court of the lord king
Gregorius Basset et Johanna Hastings executores Willelmi Stuart sunt Gregory Basset and Joanna Hastings are the executors of William Stuart

These personal names decline like third declension nouns:

Agnes, Agnetis (f.) Agnes
Johannes, Johannis (m.) John
Mathildis, Mathildis (f.) Matilda
Simo, Simonis (m.) Simon
predictus abbas Johannes hoc manerium tenet The aforesaid Abbot John holds this manor.
Simo filius et heres predicte Agnetis est et etatis decem annorum est Simon is the son and heir of the aforesaid Agnes and is [of] the age of ten years.

A phrase that you will often see at the beginning of royal documents is

Willelmus dei gratia rex William by the grace of God king gratia, -e (f.) grace
Maria dei gratia regina Mary by the grace of God queen
ego Johannes dei gratia rex terram abbati Simoni hac carta do et confirmo I, John, by the grace of God king, give and confirm the land by this charter to Abbot Simon

Genitive plural ‘-ium’

Some third declension nouns end ‘-ium’ in the genitive plural.

For example pars, partis (f.) part; civis, civis (m.) citizen

summa partium the sum of the parts summa, -e (f.) sum

These and other irregular nouns are noted in our grammar resource and Latin word list.

Third declension adjectives

These have the same endings as third declension nouns except that adjectives have

  • ‘-i’ for ablative singular
  • ‘-ium’ for genitive plural
  • ‘-ia’ for nominative, vocative and accusative neuter plural

There are two main forms of third declension adjectives.

1. Masculine and feminine are same; neuter is different.

Masculine and Feminine Neuter

Case Singular Plural Singular Plural
Nominative omnis omnes omne omnia
Vocative omnis omnes omne omnia
Accusative omnem omnes omne omnia
Genitive omnis omnium omnis omnium
Dative omni omnibus omni omnibus
Ablative omni omnibus omni omnibus
communis , -e common
fidelis, -e faithful
finalis, -e final
legalis, -e lawful
parochialis , –e parochial, parish
totalis, -e total
summa totalis sum total (used in accounts)
hec est finalis concordia this is the final concord
lego terram ecclesie omnium sanctorum I leave the land to the church of All Saints

2. Masculine, feminine and neuter are the same in the nominative

These are declined in our grammar resource.

ingens, ingentis huge
presens, presentis present
sapiens, sapientis wise
vetus, veteris old

The nominative and genitive forms of these are given in our Latin word list.
They take the same endings as omnis.

confirmamus hac presenti carta domine
Mathildi ius curiam tenere
We confirm by this present charter to the
lady Matilda the right to hold a court.

Did you notice the use of tenere to mean ‘to hold’?


Are you confident with

  • the genitive singular ending of third declension nouns?
  • how to decline rex?
  • which three endings are different in third declension adjectives and nouns?

What next?