A dictionary is typically found in one volume that contains tens of thousands of words. A dictionary is more commonly used to verify the meaning of a word.
An encyclopedia contains multiple volumes and in-depth explanations of words and concepts. An encyclopedia is used to gain a deeper understanding of that word.
A thesaurus is a book that lists words in groups of synonyms and related
concepts.
A glossary is an alphabetical list of terms or words found in or relating to a specific subject, text, or dialect, with explanations; a brief dictionary.
