Use an online thesaurus to find synonyms for a given word. Synonyms are words that have the same or a similar meaning. A thesaurus may also provide information about parts of speech, and antonyms of the word.
The thesaurus at Thesaurus.com includes information about the various meanings a word may have, and what may be considered synonymous with it in each sense.
Use a thesaurus to avoid repetition in writing. When deciding on a word to use, make sure to check its meaning in the dictionary. Some words are roughly synonymous but also have nuanced differences that can change a sentence's meaning.