Adjectives: Form Notes
Most adjectives behave like nouns of the first/second or third declension and agree with their noun in gender, number, and case — bonus puer, bona puella, bonum dōnum.
This page is the catch-all for the rest: the irregulars, the indeclinables, the defectives, and the adjectives that simply refuse to commit to a gender.
You'll meet vetus, veteris (an old third-declension form), plūs (which is a noun in the singular and an adjective in the plural), and oddities like frūgī and nēquam that never decline at all.
The point isn't to memorize every quirk — it's to recognize one when it shows up so the form doesn't trick you.
Most adjectives match their noun in three ways. The exceptions on this page break one or more of those rules.
The five categories of exception (variable, indeclinable, defective, common-gender, irregular paradigm) all show up in the canonical authors — recognize them, don't memorize them.
| Case | M./F. Sing. | N. Sing. | M./F. Plur. | N. Plur. |
|---|---|---|---|---|
| Nom. | vetus | vetus | veter-ēs | veter-a |
| Gen. | veter-is | veter-is | veter-um | veter-um |
| Dat. | veter-ī | veter-ī | veter-ibus | veter-ibus |
| Acc. | veter-em | vetus | veter-ēs | veter-a |
| Abl. | veter-e | veter-e | veter-ibus | veter-ibus |
| Case | Singular (neuter noun) | Plural (adjective) |
|---|---|---|
| Nom. | plūs | plūrēs (m./f.), plūra (n.) |
| Gen. | plūris | plūrium |
| Dat. | — | plūribus |
| Acc. | plūs | plūrēs (m./f.), plūra (n.) |
| Abl. | plūre | plūribus |
See It In Action
— B. G. i. 43
Notice veterēs uses the third-declension plural ending -ēs for masculine/feminine — same form for both genders, no -us/-a/-um split.
— Sall. Cat. 42
Plūs in the singular is a neuter noun, not an adjective — "more of fear, more of danger." The genitives timōris and perīculī depend on it.
— Plin. Ep. i. 21
Frūgī never changes — it's the same form whether the subject is one slave or many, masculine or feminine. Originally a dative ("useful for service"), it froze.
Singular plūs is a noun taking a partitive genitive; plural plūrēs/plūra is a normal adjective.
"more of X" — takes a genitive
plūs vīnī
more wine (lit. "more of wine")
agrees with its noun normally
plūrēs hostēs
more enemies
Tip: Ask: is the noun next to plūs in the genitive? If yes, plūs is the noun and the noun is partitive.
In Sallust's plūs timōris quam perīculī effēcerant ("they had produced more fear than danger"), why is timōris in the genitive?
Study Tips
- •When an adjective doesn't change to match its noun (frūgī, nēquam), don't fight it — note it's indeclinable and read on.
- •Watch for plūs in the singular: it acts like a neuter noun ("more of X"), not a normal adjective. Plūs vīnī = "more wine," literally "more of wine."
- •Common-gender adjectives like adulēscēns and senex keep one form for masculine and feminine — let the article-less Latin context tell you who's meant.
- •If you only learn one irregular paradigm here, learn vetus — it appears constantly in Caesar (vetus bellī gloria, veteribus cōpiīs).