Latin Adjectives

Latin adjective declensions (1st-2nd and 3rd), comparison of adjectives (positive/comparative/superlative), and irregular comparatives including bonus/melior/optimus.

Latin adjectives must agree with the nouns they modify in gender, number, and case — but they do not need to be in the same declension as the noun. An adjective from the 1st-2nd declension can modify a 3rd-declension noun.

1st–2nd Declension Adjectives (bonus, bona, bonum)

The most common adjective type. Masculine follows 2nd declension (-us/-er); feminine follows 1st declension (-a); neuter follows 2nd declension (-um).

Case Masc. (2nd) Fem. (1st) Neut. (2nd)
Nom. sg. bonus bona bonum
Gen. sg. bonī bonae bonī
Dat. sg. bonō bonae bonō
Acc. sg. bonum bonam bonum
Abl. sg. bonō bonā bonō
Nom. pl. bonī bonae bona

-er adjectives (2nd decl. masc.): pulcher, pulchra, pulchrum (beautiful) — drops -e- in oblique cases; miser, misera, miserum (wretched) — keeps -e-. Check the feminine/neuter form to know which.

3rd Declension Adjectives

Three subtypes based on number of nominative singular forms:

Three-Termination (separate forms for m/f/n in nom. sg.)

celer, celeris, celere (swift):

  • Masc. nom. sg.: celer; Fem.: celeris; Neut.: celere
  • Gen. sg. all genders: celeris
  • Declines otherwise as 3rd decl. i-stem

Two-Termination (one form for m/f, another for n)

fortis, forte (brave) — most common type:

  • Nom. sg. m/f: fortis; Neut.: forte
  • Gen. sg.: fortis; Dat./Abl. pl.: fortibus
  • Acc. sg. masc.: fortem; Neut.: forte

One-Termination (same form for all three genders)

felix, felicis (happy); prudens, prudentis (prudent):

  • One nom. form for all genders
  • Gen. sg. is the key to the stem: fēlic-, prūdent-
  • Abl. sg.: -ī (attributive) or -e (predicative)

Comparison of Adjectives

Regular Comparison

Degree Suffix (m/f) Neuter Example (longus)
Positive (base) (base) longus, -a, -um
Comparative -ior -ius longior, longius
Superlative -issimus/-a/-um same longissimus, -a, -um

Comparative declines as 3rd-declension adjective (one termination: longior, longior, longius). Superlative declines as 1st-2nd declension (longissimus, -a, -um).

Special Superlative Rules

  1. Adjectives ending in -er: superlative = -errimus (double r)

    • celer → celerrimus (swiftest)
    • pulcher → pulcherrimus (most beautiful)
    • miser → miserrimus (most wretched)

  2. Six adjectives ending in -ilis: superlative = -illimus (double l)

    • facilis → facillimus (easiest)
    • difficilis → difficillimus (most difficult)
    • similis → simillimus (most similar)
    • dissimilis → dissimillimus
    • gracilis → gracillimus
    • humilis → humillimus

Irregular Comparisons

Positive Comparative Superlative Meaning
bonus melior, melius optimus, -a, -um good / better / best
malus peior, peius pessimus, -a, -um bad / worse / worst
magnus maior, maius maximus, -a, -um great / greater / greatest
parvus minor, minus minimus, -a, -um small / smaller / smallest
multus plūs (n. only) plūrimus, -a, -um much / more / most
multī (pl.) plūrēs, plūra plūrimī, -ae, -a many / more / most

Plūs in singular is a neuter noun (not an adjective): plūs vīnī — "more wine" (partitive genitive).

Comparison of Adverbs

Adverbs formed from adjectives:

  • 1st/2nd decl. adj.: adverb ends in -ē: longē (far), bonē... wait: bene (well)
  • 3rd decl. adj.: adverb ends in -iter: fortiter (bravely)
  • Comparative adverb = neuter comparative of the adjective: longius (farther), melius (better)
  • Superlative adverb = superlative stem + -ē: longissimē (farthest), optimē (best)

Special: Periphrastic Comparison with magis/maximē

Adjectives ending in -eus, -ius, -uus (e.g., idōneus, egregius, assiduous) form comparisons periphrastically:

  • Comparative: magis idōneus — "more suitable"
  • Superlative: maximē idōneus — "most suitable"

Reference