Reference tables: adjective declensions

[1] 1^st / 2^nd declension adjectives (1)

[i] These adjectives have the nominative singular endings -us, -a, -um and decline in exactly the same way as 1^st and 2^nd declension nouns. The term ‘2-1-2’ is also used to describe them since:

the masculine adjective has the same endings as a 2^nd declension masculine noun: 2

the feminine adjective has the same endings as a 1^st declension feminine noun: 1

the neuter adjective has the same endings as a 2^nd declension neuter noun: 2

[ii] Only the masculine vocative singular is listed with a separate ending; in the plural and in all other adjective declensions the vocative singular is the same as the nominative singular, the vocative plural the same as the nominative plural.

[2] 1^st / 2^nd declension adjectives (2) adjectives in -er

1^st / 2^nd declension adjectives, like some 2^nd declension masculine nouns, can end in -er. These will also decline in exactly the same way and, as with this noun type, some lose the /e/ of the nominative singular when endings are added, and some retain it.

[3] 1^st / 2^nd declension adjectives (3) -īus / -ī

There are nine adjectives which are 1^st / 2^nd declension but – in the genitive and dative singular only – they have different endings:

genitive singular: -īus; dative singular: -ī

Two examples are given below. Further information is at:

https://adckl.blogspot.com/2025/04/190725-level-3-pronominal-adjectives.html

[4] 3^rd declension adjectives

[i] The adjectives of the 3^rd declension have sub-categories based on the number of endings (in grammar most often called ‘terminations’) which the adjective has in the nominative singular.

1 termination: sapiēns [m/f/n]; the same form for all three genders

2 terminations: fortis [m/f], -e [n]; the same form for masculine / feminine, and a separate form for neuter

3 terminations: ācer [m] ācris [f] ācre [n]; three separate forms for all three genders

[ii] At first sight – especially since there are three tables listed – it seems that there are a large number of endings to learn. However, all the adjectives share the same endings apart from:

(1) the nominative singular

(2) the neuter accusative singular: always the same as the neuter nominative singular (marked in yellow)

(3) the neuter nominative and accusative plural: -ia (marked in yellow)

[iii] The accusative plural of masculine and feminine adjectives has an alternative ending: -īs.

[iv] You will come across a few 3^rd declension adjectives that have [a] the neuter nominative plural in -a [b] the ablative singular in -e and [c] the genitive plural in -um; these are known as non i-stem adjectives (marked in yellow), for example:

nominative singular: pauper (poor)

ablative singular: paupere

neuter nominative / accusative plural: paupera

genitive plural: pauperum

[iv] Some 3rd declension adjectives, like 3rd declension nouns, undergo a stem change.

(1) Most stem changes occur in adjectives of one termination. That stem change, as with 3^rd declension nouns, is usually indicated by the inclusion of the genitive singular in vocabulary lists and dictionaries:

sapiēns, sapientis (wise); audāx, audācis (bold); dīves, dīvitis (wealthy)

Once endings are added, the stem change applies to all forms of the adjective apart from the neuter nominative and accusative singular, which are always identical.

(2) Other 3^rd declension adjectives may also undergo a stem change e.g. ācer, ācris, ācre; here the change applies once endings are added even to the nominative singular. Again, that change will apply to all forms of the adjective apart from the neuter nominative and accusative singular, which are always identical.