Whether they were 1st and 2nd declension words like planus or 3rd declension words like fortis, most Latin adjectives took their comparative and superlative forms according to regular and consistent rules. Thus, “flat, flatter, flattest” was planus, planior, planissimus; and “strong, stronger, strongest” was fortis, fortior, fortissimus. This feature of Latin adjective morphology has had very little effect on English. However, in the forms planissimus and fortissimus you may recognize the origins of the Italian pianissimo and fortissimo, musical terms (abbreviated as pp and ff) that mean “very softly” and “very loudly” (“very strongly”).
Several irregular Latin comparative and superlative forms have left their mark on English. In the Indo-European language family, irregular comparison is a feature of the most commonly used adjectives: consider E “good, better, best” or “bad, worse, worst.” A selection of irregular Latin comparatives and superlatives is given here:
|LATIN ADJECTIVES||ENGLISH MEANING||ENGLISH DERIVATIVES|
|bonus, melior, optimus||good, better, best||ameliorate, optimist|
|malus, pejor, pessimus||bad, worse, worst||pejorative, pessimist|
|magnus, major, maximus||big, bigger, biggest||major, majority, maximum|
|parvus, minor, minimus||small, lesser, least||minor, minus, minimum|
|multus, plus, plurimus||much, more, most||plus, plural, plurality|
Read that list through for general interest; you are not expected to commit it to memory. Other irregular Latin comparatives have entered English without change; among these are interior (“inner”), exterior (“outer”), superior (“higher”), inferior (“lower”), prior (“former”), posterior (“later”), ulterior (“farther”), junior (“younger”), senior (“older”). Their corresponding superlatives include extremus (“outermost”), supremus or summus (“highest”), and ultimus (“farthest”).