Legal Dictionaries and Thesauri

Legal dictionaries provide definitions of legal terms, phrases, maxims, and Latin legal terms. The more comprehensive dictionaries provide citations to cases and legal encyclopedias, as well as A.L.R. annotations. Pronunciation guides and historical derivations are also included. Compact dictionaries only define essential or basic legal terms.

Thesauri provide synonyms, antonyms, and associated concepts, and often basic definitions are given.

Dictionaries and thesauri have two primary uses.

1. Many legal terms have meanings that differ from their non-legal connotations. You should look up your most important legal research terms in a law dictionary to make sure that you understand them.
2. These tools can help you identify additional research terms.

First choose a suitable dictionary or thesaurus. If you are seeking a basic definition of a common legal term, consult a compact dictionary. If you are seeking a more complete definition of a less common term or legal phrase, consult one of the full-size dictionaries. If you are seeking a wider range of related terms and synonyms, consult a thesaurus.

It is better to cite a primary authority providing a definition than a dictionary. Sometimes, however, no definition exists in the primary authority within your jurisdiction, so you must cite a secondary source like a dictionary.

Examples of citations based upon Rule 15 of The Bluebook:

Ballentine's Law Dictionary 640 (3d ed. 1969).

Black's Law Dictionary 977-978 (9th ed. 2009).

Daniel Oran, Oran's Dictionary of the Law 278 (4th ed. 2008).

If you cannot find your term or need a more detailed definition, you may wish to consult a specialized legal dictionary. Specialized legal dictionaries exist in many fields including business law, constitutional law, and international law. There are also special purpose dictionaries, including dictionaries of abbreviations.

Legal usage texts resemble dictionaries and provide definitions while addressing stylistic choices in legal writing.