Comparatives (-ior, -ius) and superlatives (-issimus) compare; "than" is quam or a plain ablative.
Forms: comparative adjective -ior (m./f.), -ius (n.), gen. -ioris; comparative adverb -ius. Superlative -issimus, -errimus (miserrimus), -illimus (facillimus); adverb -issime. Irregular: melior, pejor, major, minor, plus; optimus, pessimus, maximus, minimus, plurimus; superior "higher".
"Than" is quam + the same case as the first thing compared (graviora … quam quae per iram), or the ablative without quam: Nihil homine illo miserius "nothing more wretched than that man", voluptate ac dolore omni superiorem "above all pleasure and pain".
quam + superlative means "as … as possible": quam diutissime "as long as possible", quam celerrime "as fast as possible". quisque + superlative means "all the …": minutissima quaeque "even the smallest things".
On its own a comparative may mean "rather, too", and a superlative "very". The amount of difference is in the ablative: multo "by much", paulo "a little".