Human: I want to learn about the different types of dictionaries. What's the difference between a dictionary and a thesaurus? Assistant: 
A dictionary is a collection of words and their definitions, while a thesaurus is a collection of synonyms and antonyms for a given word. Dictionaries are often used as references to look up words in order to find their meaning or usage, while thesauruses are usually used to expand vocabulary by providing alternative words for a particular word.