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Primary vs Secondary Legal Research

The materials used for legal research are generally divided into two broad categories: primary sources and secondary sources.  Primary legal sources are the actual law. Secondary sources provide commentary and background information on the law and can point you towards useful primary sources. However, they are not actual law.  The table below lists examples of each.



(either federal or state)   

Legal dictionaries 

Statutes; municipal codes

(laws enacted by legislatures); (enacted by local councils) 

Legal encyclopedias and digests   


(opinions handed down by courts) 

Law reviews and journals 

Rules and Regulations

(established by administrative government agencies)   

Legal treatises, nutshells, hornbooks, deskbooks     
Treaties Manuals and guides on how to practice law

Secondary sources are generally not binding in courts, although you may cite secondary sources in a memorandum or article when you wish to provide the reader with a more in-depth explanation of a topic.

It is a good idea to begin your research with secondary sources, especially if you are researching a topic you do not know well. Since secondary sources use primary sources as the basis for their discussion, looking at the primary sources referenced in a secondary source (cases, statutes, regulations, etc.) will provide you with an excellent basis from which you can begin analyzing and applying the law in that area.

  • The best way to begin research in a secondary source is by looking at its index and/or table of contents.
    • Print secondary sources will almost always have an index and/or table of contents of some kind, whether it is for a single work or larger set.
    • Not all online materials currently have indices and tables of contents, although that is changing as the amount of online content increases.
  • Once you have located a relevant section, be sure to read it in its entirety so you understand the context in which the material is being presented. Taking a few sentences of the material out of context can greatly alter its meaning. Always read the full text of the material before relying on the information or drawing any conclusions.

Using secondary sources can be somewhat complex due to the variety of secondary sources available and the fact that each is organized somewhat differently. The rest of this page provides access to various online resources for your research.     

Legal Dictionaries

Black's Law Dictionary is considered by many to be the preeminent legal dictionary for American Law. It can be found among the Library’s print collection (REF KF156 .B53 2014) and is also available electronically on Westlaw.  With over 55,000 law-related words and phrases, it is touted as “the most practical, comprehensive, scholarly, and authoritative law dictionary ever published.”

A number of other legal dictionaries can also be found online, and without having to subscribe to such services as Westlaw. Below is a curated list of legal dictionaries (and glossaries) that are accessible online at no cost. Bear in mind, however, that not all Internet sources are updated regularly, URLs change, and links rot. It is best to check for accuracy and current information.

Legal Dictionaries & Glossaries

Online Legal Reference

Legal Research Websites

A little bit of everything for everyone.

Paralegal: Research Help