123. In Latin, as in English, there are three degrees of comparison: the Positive, the Comparative, and the Superlative.
124. The Comparative is regularly formed by adding -ior (neuter -ius),1 the Superlative by adding -issimus (-a, -um), to the stem of the Positive, which loses its final vowel.
Note— A form of diminutive is made upon the stem of some comparatives.
grandius-culus a little larger (see § 243).
a. Participles when used as adjectives are regularly compared.
125. Adjectives in -er form the Superlative by adding -rimus to the Nominative. The comparative is regular.
ācer (keen), ācrior, ācerrimus
miser (wretched), miserior, miserrimus
a. So vetus (gen. veteris) has superlative veterrimus, from the old form veter and mātūrus, besides its regular superlative (mātūrissimus), has a rare form mātūrrimus.
For the comparative of vetus, vetustior (from vetustus) is used.
126. Six adjectives in -lis form the superlative by adding -limus to the stem clipped of its final -i-. These are facilis, difficilis, similis, dissimilis, gracilis, humilis.
facilis (easy), facilior, facillimus [stem facili-]
127. Compounds in -dicus (saying) and -volus (willing) take in their comparison the forms of the corresponding participles dīcēns and volēns, which were anciently used as adjectives.
maledicus (slanderous), maledīcentior, maledīcentissimus
malevolus (spiteful), malevolentior, malevolentissimus
a. So, by analogy, compounds in -ficus.
māgnificus (grand), māgnificentior, māgnificentissimus
idōneus (fit), magis idōneus, maximē idōneus.
Note— But pius has piissimus in the superlative, a form condemned by Cicero, but common in inscriptions; equally common, however, is the irregular pientissimus.