-ly quickly, rationally
1) There are irregural adverbs that aren’t different from adjectives: fast-fast, hard-hard, late-late, early-early + good-well
2) Sometimes you think you need an adverb, but it’s an adjective. *It is so important! (not so importantly)
3) You use an adjective after verbs of feelings: taste, sound, look, smell. *It tastes good. It smells fine.