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Secondary Sources

This guide will provide descriptions of many different kinds of secondary sources as well as tips on how to find and use them.


Legal encyclopedias, dictionaries and thesauri are similar to their general counterparts. This section will describe how they are used by legal researchers and will familiarize you with specific examples of each.


Legal encyclopedias are used to orient the researcher to unfamiliar areas of the law, and provide fairly general overviews of a large number of legal topics. They are a good place to start because they will provide a context for more specific research, and their broad nature helps ensure the researcher is aware of the scope of the issues being researched.

Encyclopedias should never be cited as sources of the law, but they can be helpful in directing the researcher to primary sources. Most legal encyclopedia articles focus on case law, rather than statutory law, and will include citations to relevant cases. Because of their general nature, encyclopedias are not always the best source for jurisdiction specific primary law sources, but often the citations provided are a good start for finding similar law in a particular jurisdiction.

The two major legal encyclopedias covering U.S. law are American Jurisprudence 2d (Am.Jur.) and Corpus Juris Secundum (C.J.S.). Am.Jur. articles are often shorter, and focus on cases the editors determine to be particularly important. C.J.S. articles tend to be longer and more comprehensive. Because C.J.S. is published by Thompson Reuters, it includes West Digest topics and keycite references to help you find related materials in Westlaw and other Thompson Reuters products.
Am. Jur. also publishes topical encyclopedias, which are designed to aid practitioners in more specific areas of the law. These include Am. Jur. Forms, Am. Jur. Proof of Facts, and Am. Jur. Trials. These are designed to provide more technical assistance in areas like trial preparation and finding government and business forms, and are structured less like a traditional encyclopedia.

Some states also have encyclopedias containing information specific to state laws. These encyclopedias vary in quality, and are useful for research in a particular jurisdiction.

General searching advice

Encyclopedias are best used as a starting point, and will often not be specific enough to answer nuanced questions. If you are looking for something similar to an encyclopedia entry on a legal topic that is too specific to be covered in a legal encyclopedia, a good next step is to look for an American Law Reports annotation on your topic.

If you are using an encyclopedia to find primary law, it is very important to make sure that the law cited in your article hasn’t changed by using a service like Shepard’s or Key Cite.


The online editions can be searched by keyword, via the index or by browsing the table of contents.

The table of contents is most useful when you have a general idea of the area you’re researching, because it allows you to go from broad topics to specific articles based on the topic, and it makes it easier to see what else is available under that subject heading that you might want to examine later.

Finding your term in the index is often the fastest way to find an article in an encyclopedia, even online. By searching the index instead of the full text of the dictionary, you will have fewer unrelated results.

Keyword searching can be useful for finding references to obscure terms, or for finding materials when you don’t know what terms they would be listed under in the index.

American Jurisprudence 2d on Westlaw, Lexis+, and Nexis Uni.
Corpus Juris Secundum on Westlaw

In Print

The print editions are best searched by using the index, which is contained in separate volumes at the end of the series. Find your topic in the index, and then find the volume or volumes that contain the articles you need.  

Be sure to check for updates to your article in the pocket part at the end of the volume. The major encyclopedias are updated quarterly, and checking the pocket part will alert you to new developments in the law.

American Jurisprudence 2d
LAW REFERENCE 2nd floor  KF 154 .A52232

Corpus Juris Secundum (through 2011)
LAW STACKS 2nd floor  KF 154 .C422

Dictionaries and Thesauri

Legal dictionaries define terms as they are used in the law. A legal dictionary will define terms more precisely than a general dictionary, and it will include latin phrases and legal abbreviations. Lawyers use legal dictionaries to look up unfamiliar terms, check to make sure they are using a term correctly, and to persuade a court to interpret a term in a favorable way.

If you’re running a keyword search and the results aren’t what you expected, you can use a dictionary to make sure the term you’re using means what you think it does.

The legal dictionary most commonly used by attorneys and courts is Black’s Law Dictionary. Older dictionaries, such as Bouvier’s Law Dictionary or older editions of Black’s, are sometimes used to trace the historical meaning of a term.  

Garner’s Dictionary of Legal Usage is a combination of a legal dictionary and a style guide, and is primarily devoted to helping legal writers use legal words effectively.  This dictionary is especially useful for drafters of legal documents and students interested in usage.

Another resource that is similar to a dictionary is Words and Phrases, which includes entries on how terms have been defined by courts and statutes, including citations to primary authority. Knowing how terms have been defined in primary law in different contexts can be very helpful, especially if that primary law is binding in your jurisdiction.

Legal thesauri are useful for finding terms for legal concepts and for identifying additional search terms to ensure a comprehensive search. If you are doing a keyword search or attempting to find a subject in an index and your results appear incomplete, a legal thesaurus can help you determine alternate terms to check.

Dictionaries and Thesauri Online
  • Black’s Law Dictionary is available on Westlaw
  • The Legal Information Institute’s Wex Legal Dictionary
  • Bouvier’s Law Dictionary is available in indexed and digitized form at
Dictionaries and Thesauri in Print

Black’s Law Dictionary
LAW REFERENCE 2nd floor  KF 156 .B53 2019

Garner's Dictionary of Legal Usage
LAW REFERENCE 2nd floor  KF 156 .G367 2011

Bouvier’s Law Dictionary
LAW STACKS 2nd floor  KF 156 .B6 1880

Words and Phrases
LAW REFERENCE 2nd floor  KF 156 .W67

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