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Northern Illinois University
College of Law
David C. Shapiro Memorial Law Library

Basic Legal Research

Legal Dictionaries

Black's Law DictionaryLegal dictionaries are useful because the legal definition of a term will often differ from the non-legal definition of a term. During the research process, look up terms you encounter to verify that your interpretation of the word is correct.

  • The Law Library has several print legal dictionaries available. One of the most frequently used is Black's Law Dictionary, 10th ed. (copies on Reserve and located elsewhere in the library)
  • The major legal databases (Bloomberg, Lexis Advance, Westlaw) have online legal dictionaries (login required to access)
  • has a free online legal dictionary at
  • Words and Phrases is a useful source similar to a dictionary. It provides judicial definitions of legal and non-legal terms. Information is compiled from headnotes containing judicial definitions. It is useful for discovering if any court, or a specific court, has ever defined a term or phrase. The Law Library's print copy (KF 156 .W57) is no longer updated as of 2015, but an up-to-date online version is available on Westlaw.

Legal Terminology: General Terms

Analogize: To take the facts, rationale or argument of a written decision and explain how the argument relates to your case/issue.

Citation: A reference to a legal precedent or authority (primary or secondary) such as a case, statute or treatise. Case citation: The alpha numeric identifier provided to enable researchers to locate written decisions. The format usually consists of a volume number, the abbreviated reporter name, and a page or paragraph number. (e.g. 268 N.E.2d 1247)

Citators: A tool used in legal research to update legal authorities by listing their subsequent history and treatment. Also provide additional research references to primary and secondary resources citing your original document.

Civil Law: The body of law imposed by the state; the law of civil or private rights; a civil law system relies on codes that provide explicit rules of a situation. A judge's decision in a civil law system does not become binding or form a precedent. Many European countries are civil law countries.

Constitution: A type of primary authority that is a set of principles that a country or state is governed by. Constitutions generally establish the branches of government, the scope of powers for each branch, and a set of guaranteed civil rights and civil liberties.

Criminal Law: The body of law defining offenses against the community at large, regulating how suspects are investigated, charged and tried, and establishing punishment for convicted offenders.

Court Rules: Rules that control the operation of the courts and the conduct of the litigants appearing before the court.

Distinguishing an Authority: Taking the facts, rationale or arguments of a written decision or other primary authority and showing the differences between that authority and your case, even if on the surface they seem similar.

Federal Jurisdiction: A federal court's power to hear matters. Under this type of jurisdiction federal courts may decide a question of civil and/or criminal federal law.

Index: An alphabetical listing of items (topics or names) available in the resource along with an indication of where each item may be found within the work. This finding tool is available in both print and electronic resources.

Hypothetical: Discussion of a legal principle based on a fictitious or assumed set of facts.

Mandatory (Binding) Authority: A primary legal authority that is binding on a court. Jurisdiction and court level determine whether a primary legal authority is mandatory or persuasive.

Moot Court: A fictitious court held, usually in law schools, to argue hypothetical cases, especially at the appellate level.

Persuasive Authority: A primary or secondary authority. The legal authority is not binding on a court, but the court may still rely on the authority when making its determination. Jurisdiction and court level determine whether a primary legal authority is persuasive or mandatory/binding. Secondary authority is always only persuasive.

Pinpoint Citation: The page on which a quotation or relevant passage appears, as opposed to

the page on which a case or article begins.

Procedural Law: Rules that describe the steps for having a right or duty judicially enforced,

as opposed to the law that defines the specific rights and duties themselves.

Primary Legal Authority: Authority that issues directly from a lawmaking body such as constitutions, legislation, regulations, and the reports of litigated cases (court opinions) among others.

Relevance: Relation or pertinence to the issue at hand.

Relief: The compensation (monetary or other- e.g., injunction) or benefit that a party asks of another party, sometimes received through settlement and other times received through the courts.

Secondary Legal Authority: Authority that explains the law but does not itself establish the law, such as a treatise, annotation, or law review article among others.

State Jurisdiction: A state court's power to hear matters. Under this type of jurisdiction state courts may decide a question of civil and/or criminal state law.

Socratic Method: A technique of law school instruction, whereby a professor questions one or more students, building on each answer with another question.

Substantive Law: The part of the law that creates, defines and regulates the rights, duties and powers of parties.

Table of Contents: Usually located at the beginning of the work, it provides a list of chapters/sections within the work, often in outline form, and the page numbers where the topics for each chapter/section begin. Some resources provide tables of contents for each chapter. Electronic resources provide them through a separate link. This finding tool is available in both print and electronic resources.

Uniform Laws: An unofficial law proposed as legislation for all the states to adopt exactly as written, the purpose being to promote greater consistency among the states.

Legal Terminology: Case Law

Appeal: To seek review by a higher court. (e.g. appeal trial court decisions to the appropriate higher court; appeal appellate court decisions to the appropriate highest court.)

Appellant: One who brings the appeal of the lower court decision (the loser in the lower court).

Appellate Briefs: Written argument submitted to the appellate court in support of a position on appeal (not the same as a case brief).

Appellee: One against whom the appeal is brought and must respond to the appeal (the winner in the lower court). Also called respondent.

Case: Generally used in law to refer to the written decision of a court.

Case Law: All reported decisions within a jurisdiction. May consist of common law decisions as well as judicial decisions interpreting statutes, regulations, constitutions etc.

Case Reporters: Court opinions that are gathered together and published in chronological order. The books containing these cases are called case reporters. Even though most cases are available online, they are still organized and cited to according to the print reporter system. Cases are primary sources regardless of publication in an official or unofficial reporter, the case decision is the primary source. Case reporters can be official or unofficial.

  • Official Reporter: The governmentally approved publication reproducing reported cases within a given jurisdiction. The official reporter is the reporter that should be cited when submitting documents to the court.
  • Unofficial Reporter: Reporters published by commercial publishers (West, Lexis, BNA) in either print or online formats, reproducing the reported decisions within a given jurisdiction. Commercially published reporters are considered unofficial reporters.

Citator: A tool used in legal research to update legal authorities by listing their subsequent history and treatment. With case law, legal citators indicate when a case has been cited by a later case, and what effect, if any, the later citation had on the original case.  The three main citators are Shepard's on Lexis, KeyCite on Westlaw and Bcite on Bloomberg Law.

Common Law: The body of judge-made law having no basis in statutes. NOTE: Case law that interprets a statue is NOT common law.

Common Law Tradition: The basis for the American legal system where courts create rules called common-law rules and those rules govern future cases in that particular area. For example, Tort cases are governed by common law rules.

Concurring Opinion: A separate written opinion explaining a vote cast by one or more judges in favor of the judgment reached, often on grounds different from those expressed in the opinion explaining the judgment.

Defendant: A person sued in a civil proceeding or accused in a criminal proceeding.

Dicta: A comment by a court that is unnecessary to a decision and therefore not precedential. There are several types of dicta in Black's. You do rely on judicial dictum, but dicta is actually short for obiter dictum. Judicial dictum is considered binding by courts while obiter dictum is not.

Digest: A case finding tool that organizes cases by subject. Within each subject digests provide summaries of cases that discuss the law on that subject. Digests allow you to find cases on a particular point of law in a particular jurisdiction. Online services also provide digests for particular topics.

Dissenting Opinion: An opinion by one or more judges who disagree with the decision reached by the majority.

Docket Number: Courts assign each newly filed action with a number. The number usually refrences the year the case was commenced followed by a series of numbers or letters that represent the type of action (civil, criminal, family court, etc.) or location of filing.

Federal Circuit Courts: The appellate court level in the federal court system. There are 13.

Federal District Courts: The trial court level in the federal court system. There are 94.

Headnote: A brief summary of a specific point of law decided in a case. Headnotes appear before the judicial opinion, and are generally written by a publisher's editors. Headnotes are a great research tool, but are not considered legal authority and should never be cited to.

Illinois Circuit Courts: The trial court level in the Illinois state court system. There are 24.

Illinois District Courts: The appellate court level in the Illinois state court system. There are 5.

Intermediate Appellate Courts: Appellate courts that are in the middle of the judicial hierarchy in a jurisdiction, they are above the trial court and below the highest court/court of last resort. Their opinions are binding on the courts below them (trial courts).

Judge: A public official appointed or elected to hear and decide legal matters in court.

Judiciary: The branch of government responsible for interpreting the laws and administering justice; a body of judges.

Justice: A judge, especially of an appellate court.

Litigation: The process of carrying on a lawsuit; the lawsuit itself.

Litigator: A lawyer who prepares cases for trial as by conducting discovery and pretrial motions, trying cases and handling appeals; a trial lawyer.

Litigant: A party to a lawsuit.

Majority Opinion: see Opinion.

Minority Opinion: see Opinion.

Official Reporter: see Case Reporter.

Opinion: The written decision of a court.

  • Majority Opinion: An opinion joined in by more than half of the judges considering a given case.One judge writes the opinion when a majority of judges agree with the holding.
  • Minority Opinion: An opinion by one or more judges who disagree with the decision reached by the majority - also called a dissenting opinion.
  • Concurring Opinion: A judge who voted with the majority opinion, but writes separately because her reasoning is different.
  • Dissenting Opinion: A judge who writes a separate opinion where the reasoning and the holding are different from the majority.
  • Per Curiam Opinion: Literally "By the Court."  This happens when the court issues a unanimous opinion, typically on a controversial topic, so that no single author can be identified.

Opinions, unpublished: An opinion is considered published unless it is specifically designated as "unpublished."  The court typically designates an opinion as "unpublished" if it doesn't add anything new to the body of law.  Courts have different rules about whether they will accept citations to unpublished opinions. 

Parallel Citation: An additional reference to a case that has been reported in more than one reporter. Example: Morgan v. United States, 304 U.S. 1, 58 S. Ct. 773, 82 L. Ed. 1129 (1938), where 58 S. Ct. 773 and 82 L. Ed. 1129 are parallel citations to the decision cited in the official reporter at 304 U.S. 1.

Petitioner: A party who presents a petition to a court or other official body, especially when seeking relief on appeal (where the Petitioner is the Appellant).

Plaintiff: The party who brings a civil suit in a court of law.

Precedent: A decided case that furnishes a basis for determining later cases involving similar facts or issues.

Reporter: see Case Reporters.

Respondent: The party against whom an appeal is taken (appellee); the party against whom a motion or petition is filed.

Slip Opinion: The opinion issued by the court as a stand-alone document on the day it is decided, before it has been assigned a volume and page number in the official reporter.  

Star Pagination: A device, typically one or more asterisks (*), used in in cases online to designate differences in pagination of the case as it would appear in print in different reporters. 

Stare Decisis: "To stand by things decided." An American legal system doctrine of precedent under which it is necessary for a court to follow earlier judicial decisions when the same points are again in litigation.

Supreme Court: This is the court of last resort, or the highest court in the judicial hierarchy. The opinions of a supreme court are binding on all the courts below it (Trial and Appellate). Note that some jurisdictions refer to the highest court as a Court of Appeals or Court of Last Resort, e.g., in New York State the Supreme Court is not the highest court in the state.

Syllabus/Synopsis: A summary of the case.  It will usually describe the procedural posture (how the case made it to to the court) and the holding. It is not part of the official opinion.

Table of Authorities: The list of primary authorities (cases, statutes, regulations, or constitutions) and secondary authorities relied upon in the document you are viewing.

Topic & Key Number System: A proprietary system developed by West Publishing (now ThomsonReuters) to identify related cases on a similar issue.  Each headnote in cases published by West will be assigned a corresponding topic and key number.

Trial Courts: Trial courts are at the bottom of the judicial hierarchy in a jurisdiction. They are usually persuasive primary authority. Trial court opinions bind only the parties involved in the case, other trial courts hearing similar cases are not bound by the opinions, and the appellate courts in the jurisdiction are not bound by the trial court opinions.

Legal Terminology: Codes, Statutes & Administrative Law

Code: The subject arrangement of the laws or regulations of a jurisdiction.

  • Annotated Code: A publication of all the laws of a jurisdiction organized by subject matter which contains research references that include summaries of cases or citations to secondary sources that discuss that particular law. Annotated codes only contain select case law interpreting the statute, not every case ever citing the statute.
  • Unannotated Code: A publication of all the laws of a jurisdiction organized by subject matter. No research references are included in unannotated codes.

Legislative History: The proceedings leading up to the enactment of a statute. This includes hearings, committee reports, and floor debates among other resources. Legislative history is recorded so that it can be used to interpret the statute at a later date. Legislative history records are available for federal statutes. Many states keep records of legislative history, but the extent of the record varies from state to state. Legislative history is considered a primary authority.

Regulation: In administrative law, a primary authority that stems from the executive branch. It is a directive issued by a government agency that implements and/or carries out a governmental policy or program. The directive must be within the agency's statutory authority.

Session Laws: A body of statutes enacted by a legislature during a particular annual or biennial session; the books containing these statutes. Maintained in public act or public law format.

Statute: A law passed by a legislative body. Often also called laws and codes.

  • Federal Statute: Written laws passed by the United States Congress. Statutes are primary authority.
  • State Statute: Written laws passed by the state legislature. Statutes are primary authority.

Statutes at Large: An official compilation of the acts and resolutions that become law from each session of the United States Congress. They are printed in chronological order.

Statutory Annotations: In statutory research, the term is used to refer to brief summaries of court decisions interpreting and applying statutes as well as summaries of secondary materials referencing the statutory section. These summaries appear in annotated statutory compilations, after the text of individual statutes. They are also referred to as research references.

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