1
Adjectives
An adjective is a word that modifies (i.e., describes) a noun, typically indicating which one,
what kind, or how many. It agrees with that noun in gender, number, and case. As a result of
the fact that nouns and adjectives use many of the same forms, an adjective will also happen
to have the same ending as the noun it modifies in a substantial minority of examples. E.g.,
 Fēmina est alta. (The woman is tall.) The noun fēmina is feminine singular
nominative, so the adjective alta is likewise. They also happen to have the same
ending, as they are both 1st-declension words.
 Magister est altus. (The teacher is tall.) The noun magister is masculine singular
nominative, so the adjective altus is likewise. However, even though they are both
2nd-declension words, they have different endings.
 Animal est altum. (The animal is tall.) The noun animal is neuter singular
nominative, so the adjective altum is likewise. However, the noun is 3rd-declension,
while the adjective is 2nd-declension, so they have different endings.
Latin adjectives are divided into 3 categories: indeclinable, 1st and 2nd declension, and 3rd declension.
No adjectives use 4th- or 5th-declension forms.
The most important examples of indeclinable adjectives are the cardinal numbers 4 through 100.
Adjectives of the 1st and 2nd declension have 3 principal parts, representing the masculine, feminine,
and neuter singular nominative: e.g., magnus, magna, magnum. The stem (magn-) is found by
dropping the ending from the 2nd (or 3rd) principal part.
As with 2nd-declension nouns, some of these adjectives end –er in the 1st principal part. The letter e
may or may not appear in the stem as well. English derivatives will help you with this, as they
usually come from the stem rather than from the 1st principal part. E.g., liberal comes from līber,
lībera, līberum, while pulchritude comes from pulcher, pulchra, pulchrum.
These adjectives use 2nd-declension masculine endings to modify masculine nouns, 1st-declension
endings to modify feminine nouns, and 2nd-declension neuter endings to modify neuter nouns.
M.
us
ī
ō
um
ō
F.
a
ae
ae
am
ā
N.
um
ī
ō
um
ō
M.
ī
ōrum
īs
ōs
īs
F.
ae
ārum
īs
ās
īs
N.
a
ōrum
īs
a
īs
A fairly small subcategory of adjectives and pronouns are similarly irregular—for the most
part, they have 1st- and 2nd-declension forms, but they end –īus in the singular genitive and –ī
in the singular dative. These words are:
 Ūnus, Nūllus, Ūllus, Sōlus, Neuter, Alius, Uter, Tōtus, Alter—9 total. Note the
acronym: UNUS NAUTA (one sailor).
 The 5 demonstratives (hic, ille, iste, is, īdem), the intensive (ipse), the relative pronoun
(quī), the interrogative pronoun (quis), and the interrogative adjective (quī)—9 total.
 Various indefinite pronouns/adjectives built from the interrogative pronoun/adjective.
2
Adjectives of the 3rd declension come in 3 categories: 1, 2, or 3 terminations.
 Adjectives of 1 termination have 2 principal parts, representing the singular nominative and
singular genitive: e.g., ingēns, ingentis. (Notice that the definitive 3rd-declension ending, –is,
is seen in the 2nd principal part.)
 Adjectives of 2 terminations have 2 principal parts, representing the masculine/feminine
singular nominative and neuter singular nominative: e.g., brevis, breve. (Notice that, for
most such adjectives, the definitive 3rd-declension ending, –is, is seen in the 1st principal part.)
 Adjectives of 3 terminations have 3 principal parts, representing the masculine, feminine, and
neuter singular nominative: e.g., ācer, ācris, ācre.
Regardless of the number of terminations, the stem (ingent-, brev-, or ācr-) is found by dropping the
ending from the 2nd (or 3rd) principal part.
As with 1st- and 2nd-declension adjectives, some of these adjectives end –er in the 1st principal part.
Again, English derivatives will help you keep track of whether the letter e appears in the stem as
well. E.g., accelerate comes from celer, celeris, celere, while acrimony comes from ācer, ācris, ācre.
3rd-declension adjectives use I-stem forms wherever possible:
M./F.
1 termination:
2 terminations:
N.
ingēns
ingentis
ingentī
ingentem
ingēns
ingentī
M./F.
N.
ingentēs
ingentia
ingentium
ingentibus
ingentēs
ingentia
ingentibus
M./F.
brevis
M./F.
brevēs
N.
breve
brevis
brevī
brevem
breve
brevī
3 terminations:
M.
ācer
F.
ācris
ācris
ācrī
ācrem
acrī
N.
ācre
N.
brevia
brevium
brevibus
brevēs
brevia
brevibus
M./F.
ācrēs
N.
ācria
ācrium
ācribus
ācre
ācrēs
ācria
ācribus
There are 2 main exceptions to the above comment on I-stems:
 Present active participles (which are adjectives of 1 termination) don’t always have the I-stem
form in the singular ablative. E.g., the singular ablative of agēns may be agentī or agente.
 Comparative adjectives (which are adjectives of 2 terminations) don’t have any I-stem forms.
Thus, the forms of fortior include fortiōre (singular ablative), fortiōra (neuter singular
nominative/accusative), and fortiōrum (plural genitive).