Dictionaries will help you to understand the meaning and the pronunciation of words.
The Oxford English Dictionary: An excellent electronic dictionary giving the meaning, history, and pronunciation of words -- past and present -- from across the English-speaking world.
Fowler's Dictionary of Modern English Usage: In the Killam Library Reference Collection at CALL NUMBER: PE 1464 F65 2015
The Concise New Partridge Dictionary of Slang and Unconventional English (2015): An electronic dictionary containing over 60,000 slang and unconventional English words from around the English-speaking world from 1945 to the early 21st century.
Encyclopedias can be print or electronic and contain general information on many different areas of knowledge. Entries or short articles in encyclopedias are usually arranged alphabetically, from A-Z.
Credo Reference: An electronic encyclopedia containing lots of information about many, many different topics. A great source to learn the basics about a topic.
Gale Virtual Reference Library: Provides the fulltext of many different reference books, including encyclopedias, handbooks, and dictionaries in a wide range of subject areas.