Dictionaries can be a good support in all your work with text. Be certain that you use the correct term with the correct meaning. Be certain that the word you read means what you think it does. Use a dictionary!
An encyclopedia is a handy tool when you want to learn something, check something, or get an overview of the use of a term.
Dictionaries for specific knowledge-fields are placed with other books from that field in the physical library. These are some of the Dewey-numbers that might interest you:
340.03: Law
610.3: Medicine
650.03: Business management