Latin Vocabulary

While the Canadian legal system has its roots in English common law, Latin terminology remains a cornerstone of legal language. Understanding these terms is essential for interpreting legal documents, participating in courtroom proceedings, and effectively communicating with colleagues and clients.

Below are 50 Latin terms and phrases you will run into in Canadian law, each with a plain definition, an example and a quick etymology. They aren’t just relics of Roman law: courts and lawyers still use them, and knowing them makes cases and statutes a lot easier to read, whether you’re a law student, working in law, or just curious about the jargon. This page is part of my free law school resources.

Here are 50 commonly used legal Latin terms and phrases that you should know:

1. Ab Initio: From the beginning.
   Example: The contract was void ab initio because it was signed under duress.
   Etymology: Derived from “ab” meaning “from” and “initio” meaning “beginning.”
2. Actus Non Facit Reum Nisi Mens Sit Rea: An act does not make a person guilty unless there is a guilty mind.
   Example: The defendant was acquitted because actus non facit reum nisi mens sit rea; he had no knowledge of the illegal substances in his car.
   Etymology: “Actus” means act, “reum” means guilty, “nisi” means unless, “mens” means mind, and “sit rea” means is guilty.
3. Actus Reus: The physical act constituting a criminal offence.
   Example: The actus reus in the case was the defendant’s act of stealing the purse.
   Etymology: “Actus” means act and “reus” means guilty.
4. Ad Hoc: For a specific purpose or situation.
   Example: The committee was formed ad hoc to address the budget crisis.
   Etymology: “Ad” means to or for and “hoc” means this.
5. Affidavit: A written statement confirmed by oath for use as evidence.
   Example: She submitted an affidavit to support her claim.
   Etymology: “Affidare” means to pledge.
6. Amicus Curiae: A ‘friend of the court’; an impartial adviser in a case.
   Example: An amicus curiae was appointed to make submissions on the legal issue.
   Etymology: “Amicus” means friend and “curiae” means of the court.
7. A Priori: From the earlier; based on deduction or reasoning.
   Example: The scientist made an a priori assumption before conducting the experiment.
   Etymology: “A” means from and “priori” means earlier.
8. Bona Fide: In good faith; genuine.
   Example: The offer was made bona fide and was free of any intent to deceive.
   Etymology: “Bona” means good and “fide” means faith.
9. Caveat Emptor: Buyer beware; the principle that the buyer is responsible for checking the quality of goods before purchase.
   Example: The principle of caveat emptor applies when buying a used car.
   Etymology: “Caveat” means let him beware and “emptor” means buyer.
10. Certiorari: A writ by which a superior court reviews, and can quash, the decision of a lower court or tribunal.
    Example: On judicial review, the applicant asked the court for certiorari quashing the tribunal’s decision.
    Canadian note: In the US, “cert” is how cases reach the US Supreme Court. In Canada, certiorari is a remedy used mainly on judicial review; to get a case heard by the Supreme Court of Canada, you apply for “leave to appeal” instead.
    Etymology: “Certiorari” means to be informed.
11. Contra Proferentem: Against the offeror; ambiguous terms in a contract are interpreted against the party that drafted it.
    Example: The clause was vague, so the judge applied the rule of contra proferentem.
    Etymology: “Contra” means against and “proferentem” means the one bringing forth.
12. Corpus Delicti: Body of the crime; the fact that a crime has been committed.
    Example: Without a corpus delicti, the prosecution’s case was weak.
    Etymology: “Corpus” means body and “delicti” means of the crime.
13. Cui Bono: Who benefits? Often used to suggest who might be the perpetrator of a crime.
    Example: Cui bono from the destruction of the evidence?
    Etymology: “Cui” means to whom and “bono” means good.
14. De Facto: In fact, whether by right or not.
    Example: She is the de facto leader of the group, even though she hasn’t been officially elected.
    Etymology: “De” means of and “facto” means fact.
15. De Jure: According to law; by right.
    Example: He is the de jure owner of the property, as proven by the deed.
    Etymology: “De” means of and “jure” means law.
16. De Minimis Non Curat Lex: The law does not concern itself with trifles.
    Example: The judge dismissed the case, citing de minimis non curat lex.
    Etymology: “De” means of, “minimis” means trivialities, “non” means not, “curat” means cares, and “lex” means law.
17. De Novo: Starting anew; often used in the context of appellate review.
    Example: The appellate court ordered a de novo trial.
    Etymology: “De” means of and “novo” means new.
18. Duces Tecum: Bring with you; often used in the context of a subpoena for documents.
    Example: The court issued a subpoena duces tecum for the company’s financial records.
    Etymology: “Duces” means you shall bring and “tecum” means with you.
19. Ex Parte: From or on one side only, in the interest of one party.
    Example: The judge issued an ex parte order for temporary custody.
    Etymology: “Ex” means out of and “parte” means part or side.
20. Ex Post Facto: After the fact; a law that retroactively changes the legal consequences of acts done before it was passed.
    Example: The law was not ex post facto, so it did not affect prior cases.
    Etymology: “Ex” means out of, “post” means after, and “facto” means fact.
21. Fiat Justitia Ruat Caelum: Let justice be done though the heavens fall.
    Example: The judge, believing in fiat justitia ruat caelum, refused to be swayed by public opinion.
    Etymology: “Fiat” means let it be done, “justitia” means justice, “ruat” means may fall, and “caelum” means sky.
22. Habeas Corpus: A writ requiring a person to be brought before a court or judge, especially to secure the person’s release.
    Example: The prisoner filed a writ of habeas corpus to challenge his detention.
    Etymology: “Habeas” means you shall have and “corpus” means body.
23. In Camera: In private; a legal proceeding in the judge’s private chambers.
    Example: The judge decided to review the sensitive evidence in camera before making a ruling.
    Etymology: “Camera” originates from the word for “chamber,” indicating a private or secluded space.
24. In Loco Parentis: In the place of a parent.
    Example: The school acts in loco parentis when students are on a field trip.
    Etymology: “Loco” means place or stead, and “Parentis” refers to a parent, denoting substitution or acting on behalf of a parent.
25. In Re: In the matter of; concerning.
    Example: The case of In Re Smith involves an estate dispute.
    Etymology: “Re” means “thing” or “matter,” indicating the subject or focus of legal proceedings.
26. Inter Alia: Among other things.
    Example: The contract, inter alia, discussed payment terms and confidentiality.
    Etymology: “Inter” means among, and “Alia” means other things, signifying inclusion among a range of items or issues.
27. Ipso Facto: By the very fact; by the act itself.
    Example: He became, ipso facto, the leader when his predecessor resigned.
    Etymology: “Ipso” means “itself” and “Facto” means “fact,” indicating that something is true by its very nature.
28. Jus Cogens: Compelling law; a fundamental principle of international law.
    Example: The prohibition against genocide is considered jus cogens in international law.
    Etymology: “Jus” means law, and “Cogens” means compelling, indicating a principle that cannot be disregarded.
29. Lex Loci: The law of the place where the action occurred.
    Example: The lex loci of the car accident will determine which laws apply.
    Etymology: “Lex” means law, and “Loci” means place, indicating the jurisdiction where an event took place.
30. Malum In Se: Wrong in itself; an act inherently wrong.
    Example: Murder is considered malum in se.
    Etymology: “Malum” means evil or wrong, and “In Se” means in itself, indicating an act that is inherently immoral.
31. Malum Prohibitum: Wrong due to being prohibited; acts illegal by statute.
    Example: Jaywalking is malum prohibitum but not malum in se.
    Etymology: “Malum” means evil or wrong, and “Prohibitum” means prohibited, indicating an act that is wrong because it is legally prohibited.
32. Mens Rea: The mental element of a crime; criminal intent.
    Example: The prosecution must prove mens rea to secure a conviction for theft.
    Etymology: “Mens” means mind, and “Rea” means guilty, indicating the mental state of guilt.
33. Nemo Dat Quod Non Habet: No one gives what they do not have.
    Example: You can’t sell a car you don’t own; nemo dat quod non habet.
    Etymology: “Nemo” means no one, “Dat” means gives, “Quod” means what, “Non” means not, and “Habet” means have, indicating the impossibility of transferring what one does not possess.
34. Nunc Pro Tunc: Now for then; to correct an earlier ruling.
    Example: The court issued a nunc pro tunc order to correct the clerical error in the judgment.
    Etymology: “Nunc” means now, “Pro” means for, and “Tunc” means then, indicating a retroactive legal effect.
35. Per Curiam: By the court; an opinion from an appellate court.
    Example: The decision was issued per curiam, without a single judge being identified as the author.
    Etymology: “Per” means by or through, and “Curiam” means court, indicating a collective judicial opinion.
36. Per Se: By itself; inherently.
    Example: Driving with a blood alcohol concentration over the legal limit is an offence per se, even if the driver shows no signs of impairment.
    Etymology: “Per” means by or through, and “Se” means itself, indicating something that is inherently so.
37. Prima Facie: At first sight; based on the first impression.
    Example: The evidence provided a prima facie case of negligence.
    Etymology: “Prima” means first, and “Facie” means face or appearance, indicating an initial impression that is sufficient unless proven otherwise.
38. Pro Bono: For the public good; legal work done without charge.
    Example: The lawyer took on the civil rights case pro bono.
    Etymology: “Pro” means for, and “Bono” means good, indicating work done for the public benefit.
39. Pro Hac Vice: For this occasion; used for out-of-jurisdiction lawyers allowed to appear in a single case.
    Example: The visiting lawyer was admitted pro hac vice to argue one case.
    Canadian note: This is mainly a US term. In Canada, lawyers from other provinces generally practise temporarily under their law societies’ mobility rules, and each law society sets its own requirements for lawyers from outside Canada.
    Etymology: “Pro” means for, “Hac” means this, and “Vice” means turn or occasion, indicating a temporary or specific circumstance.
40. Pro Se: For oneself; representing oneself in court.
    Example: He chose to go to trial pro se rather than hire a lawyer.
    Canadian note: This is mainly a US term. Canadian courts usually call such a person a “self-represented litigant.”
    Etymology: “Pro” means for, and “Se” means oneself, indicating self-representation.
41. Quantum Meruit: As much as he/she deserved; often used in contract law.
    Example: She filed a claim for quantum meruit after the contract was terminated.
    Etymology: “Quantum” means how much, and “Meruit” means deserved, indicating a reasonable value for services rendered.
42. Quid Pro Quo: Something for something; mutual consideration for a contract.
    Example: The internship offered training and experience as quid pro quo for time and effort.
    Etymology: “Quid” means something, “Pro” means for, and “Quo” means something else, indicating a mutual exchange.
43. Ratio Decidendi: The reason for the decision; the legal principle upon which a case is decided.
    Example: The ratio decidendi of the case set a new precedent for privacy laws.
    Etymology: “Ratio” means reason, and “Decidendi” means of deciding, indicating the foundational principle of a legal decision.
44. Res Ipsa Loquitur: The thing speaks for itself; traditionally used in tort law to presume negligence.
    Example: The surgeon left a sponge inside the patient, a classic res ipsa loquitur fact pattern.
    Canadian note: In Fontaine v British Columbia (Official Administrator), [1998] 1 SCR 424, the Supreme Court of Canada said the maxim should be treated as expired in Canadian negligence law. Courts now weigh the circumstantial evidence instead, and may infer negligence from it.
    Etymology: “Res” means thing, “Ipsa” means itself, and “Loquitur” means speaks, indicating that the facts imply negligence.
45. Respondeat Superior: Let the master answer; employer liability for employee actions.
    Example: Under the doctrine of respondeat superior, the company was held liable for the employee’s actions.
    Canadian note: Canadian courts usually discuss this as “vicarious liability.”
    Etymology: “Respondeat” means let answer, and “Superior” means higher or master, indicating that the employer is responsible for the actions of the employee.
46. Stare Decisis: To stand by decisions; the doctrine of legal precedent.
    Example: The court upheld the principle of stare decisis by not overturning the earlier ruling.
    Etymology: “Stare” means to stand, and “Decisis” means decisions, indicating the practice of adhering to legal precedents.
47. Status Quo: The existing state of affairs.
    Example: The court issued an injunction to maintain the status quo until the case was resolved.
    Etymology: “Status” means state or condition, and “Quo” means existing or current, indicating the current state of affairs.
48. Sui Generis: Unique; in a class of its own.
    Example: The artwork is sui generis, unlike anything else in the genre.
    Etymology: “Sui” means of its own, and “Generis” means kind or class, indicating something unique or in a class by itself.
49. Ultra Vires: Beyond the powers; acts beyond one’s legal authority.
    Example: The CEO’s actions were deemed ultra vires and thus invalid.
    Etymology: “Ultra” means beyond, and “Vires” means strength or powers, indicating actions beyond legal authority.
50. Voir Dire: To speak the truth; the process of preliminary examination of witnesses or jurors. In Canadian criminal trials, it most often means a hearing within the trial, usually without the jury, to decide whether evidence is admissible.
    Example: The judge conducted a voir dire to determine the juror’s impartiality.
    Etymology: Strictly speaking this one is Law French, not Latin. “Voir” here does not mean “to see”: it comes from the Latin “verum,” meaning truth, and “Dire” means to say or to speak. Put together, to speak the truth.