Synonyms will generally have the same grammatical form, so the differences are to do with nuances of meaning- thesauruses usually group synonyms and near-synonyms. The choice of word is dictated by collocation, style, etc, so you need to compare words in use. Try searching a concordancer (language database) to see if a word occurs in a similar context before using it.
American English: Corpus of Contemporary American English (COCA)
British English: British National Corpus (BYU-BNC)