a. Several adjectives vary in declension: as, gracilis (-us), hilaris (-us), inermis (-us), bicolor (-órus).
b. A few adjectives are indeclinable: as, damnás, frúgí (really a dative of service, see § 382. 1. N.2), néquam (originally an adverb), necesse, and the pronominal forms tot, quot, aliquot, totidem. Potis is often used as an ind [QUERY] clinable adjective, but sometimes has pote in the neuter.
c. Several adjectives are defective: as, exspés (only nom.), exléx (exlégen) (only nom. and acc. sing.), pernox (pernocte) (only nom. and abl. sing.) and prímóris, séminecí, etc., which lack the nominative singular.
d. Many adjectives, from their signification, can be used only in the masculine and feminine. These may be called adjectives of common gender.
Such are aduléscéns, youthful; [déses], -idis, slothful; inops, -opis, poo[QUERY] sóspes, -itis, safe. Similarly, senex, old man; and iuvenis, young man, are sometimes called masculine adjectives.
For Adjectives used as Nouns, see §§ 288, 289; for Nouns used as Adjectives, s[QUERY] § 321. c; for Adjectives used as Adverbs, see § 214; for Adverbs used as Adjective see § 321. d.