1) Comparatives:

1.1) Formation of comparatives:

stem plus -ior (m. f.) -ius (n.)

1.2) Declension of Comparatives:

follows mostly the third declension

nom. -ior -ior -ius
gen. -ioris -ioris -ioris
dat. -iori -iori -iori
acc. -iorem -iorem -ius
abl. -iore -iore -iore
pl nom. -iores -iores -iora
pl gen. -iorum -iorum -iorum
pl dat. -ioribus -ioribus -ioribus
pl acc. -iores -iores -iora
pl abl. -ioribus -ioribus -ioribus

1.3) usage of comparatives:

* with quam: Hi libri sunt clariores quam illi (These books are clearer than those).

When two qualities of an object are compared, both adjectives are in the Comparative:--
longior quam latior acies erat (the line was longer than it was broad).

* without quam: Vita ejus erat brevior. (meaning "rather")

* with ablative: Consilia tua sunt clariora luce.

Where magis is used, both adjectives are in the positive:--
clari magis quam honesti (more renowned than honorable).

2) Superlatives:

2.1) formation of superlatives:

by adding -issimus -issima -issimum to the stem.

e.g. altus -a -um -> altissimus altissima altissimum

* If the adjective has -er in nom. sg. m. simply add -rimus rima -rimum to form the superlative.

e.g. acer -cris -cre -> acerrimus acerrima acerrimum.

2.2) Declension of superlatives:

follows the first and second declension as "bonus, -a, -um".

2.3) usage of superlatives:

with quam, vel, or unus:

Amicus meus erat vir quam jucundissimus. (meaning of the greatest possible degree)

vel minimus (the very least).

vir unus doctissimus (the one most learned man).

without quam: Vita ejus erat brevissima. (meaning "very" )

The Superlative of eminence often used in complimentary references to persons. It also denotes a very high degree of a quality without implying a distinct comparison: as,--mons altissimus, a very high mountain.

Superlatives denoting order and succession usually designate not what object, but what part of it.:--
summus mons (the top of the hill).
in ultima platea (at the end of the place).
prior actio (the earlier part of an action).

3) Irregular comparisons:

*special formation of seven comparatives and superlatives:
bonus -a -um (good) melior melior melius optimus -a -um
malus -a -um (bad) peior peior peius pessimus -a -um
magnus -a -um (great) maior maior maius maximus -a -um
parvus -a -um (small) minor minor minus minimus -a -um
multus -a -um (much) - - plus plurimus -a -um
- - - prior prior prius (former) primus -a -um (first)
superus -a -um (above) superior superior superius (high) supremus -a -um; summus -a -um (highest)

N.B.: Adjectives ending in -us preceded by a vowel form comparative and superlative by adding magis and maxime respectively (except those ending in -quus).
e.g.: idoneus -a -um, magis idoneus -a -um, maxime idoneus -a -um.
except: antiquus -a -um, antiquior antiquior antiquius, antiquissimus -a -um.

*inflection of "plus":

m.f. n. sg. m.f. pl.
- plus plures plura
- pluris plurium plurium
- - pluribus pluribus
- plus plures plura
- plure pluribus pluribus

*special formation of six superlatives:
facilis -e comp. facilior -us sup. facilimus -a -um
difficilis -e comp. difficilior -us sup. difficilimus -a -um
similis -e comp. similior -us sup. similimus -a -um
dissimilis -e comp. dissimilior -us sup. dissimilimus -a -um
gracilis -e comp. gracilior -us sup. gracilimus -a -um
humilis -e comp. humilior -us sup. humilimus -a -um