A thesaurus is a book that lists words alphabetically or in groups of synonyms and related concepts. In it, you can often find not only synonyms, but antonyms of many words as well.
A dictionary is a book that contains a list of words arranged alphabetically. For each word, you can see its:
definition - its meaning or meanings;
part of speech;
correct spelling;
pronunciation;
etymology - its origin of the word.
You would use the synonym finder to look for synonyms.
You would use a social studies glossary to look for definitions of terms related to the social studies.
