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A dictionary is crucial when learning a language. It contains over thousands of words that we don't know. Also, there is a thesaurus--A book that contains lists of synonyms and antonyms for a word. Words on the list have the same meaning. There are two types of dictionaries: bilingual and monolingual. Bilingual dictionaries have meanings in foreign languages while monolingual dictionaries are not. However, using monolingual dictionaries can be a tricky task for beginners. It is good to start with a bilingual dictionary if you are an absolute beginner.