There are some excellent dictionaries Online. Just ask for what you need.
A Thesaurus is a good reference for synonyms and antonyms. Even a good dictionary will sometimes have those.
synonym of adorn = array, beautify, bedeck, deck, doll up, dress up, embellish, enhance, enrich, fix up, furbish, garnish, grace, gussy up, ornament, spruce up, trim
equivalent word in French to decorate = décorer
synonyms in English FOR comprehension? sorry, but your last question is incomprehensible.
for = understanding, grasp, knowledge, command, conception, ability