ACTOR - The Law Mind Legal Dictionary

ACTORAuthored

The Law Mind • 1054 words

Definition

In legal usage, *actor* carries two distinct meanings drawn from Roman and civil law tradition, each surviving into common law contexts in different ways.

1. *Plaintiff or claimant.* In Roman civil procedure and in the civil law tradition generally, the actor is the party who institutes an action — the plaintiff, complainant, or petitioner. The term corresponds closely to the modern plaintiff in civil litigation and to the complainant in certain public proceedings.

2. *Agent or business manager.* In Roman law, actor also designated a person who acted on behalf of another in the management of affairs — a steward, agent, or representative. This included slaves appointed by their masters to conduct commercial transactions, receive and disburse funds, and maintain accounts. In this sense, the term is closer to agent or procurator than to any modern litigation term.

A third, narrower usage appears in some sources: actor as advocate or proctor in civil courts — a representative who appeared and argued on another's behalf, distinct from the party itself.

---

Common Language

Modern common usage (Wiktionary): A person who performs a role in a theatrical production, film, or television; more broadly, anyone who takes part in an action or event.

Historical common usage (Webster's 1913): "One who acts, or takes part in any affair; a doer. A theatrical performer; a stage-player." Webster's also preserves the legal senses — advocate in civil courts and one who institutes a suit — reflecting the term's longer legal currency.

The gap matters for researchers: in modern general English, *actor* means almost exclusively a performer. In legal and historical sources, particularly those drawing on Roman or civil law, *actor* means plaintiff or agent. A researcher encountering the term in a 17th- or 18th-century legal text should not assume the theatrical meaning, and should not assume the plaintiff meaning without confirming which civil law sense is operative.

---

Common Confusion

*Actor* (plaintiff) is sometimes confused with *reus* (defendant), the opposing party in the Roman procedural pairing. The maxim *actor sequitur forum rei* — the plaintiff follows the forum of the defendant or of the thing in suit — uses both terms and is a common source of confusion because *rei* is ambiguous: it is the genitive of either *res* (thing) or *reus* (defendant). Anderson and Burrill both note this ambiguity. Researchers reading this maxim in historical sources should check context to determine which sense of *rei* the author intends.

*Actor* in the sense of agent should not be conflated with *procurator*, though the roles overlap. In Roman practice, distinctions between types of representatives were technically significant; historical sources vary in how precisely they maintain these lines.

---

Why It Matters in Research

The primary research trap with *actor* is anachronism. Modern legal writing uses the term almost exclusively in the constitutional and civil rights context — "state actor," "government actor," "private actor" — a usage with no direct connection to the Roman procedural meaning. Historical sources use *actor* to mean plaintiff. These are functionally unrelated senses, and conflating them will produce misreadings.

In constitutional and civil rights research, *actor* is a term of art in its own right: whether a defendant qualifies as a "state actor" determines whether constitutional protections and Section 1983 liability attach. This modern usage is entirely absent from the historical dictionaries, which is expected — it developed through 20th-century constitutional litigation, not Roman procedure. Researchers working in the Law Mind corpus should expect to find the plaintiff sense in civil law treatises, equity materials, and sources drawing on the Institutes or the Code, and the state actor sense in materials from the post-Civil War period onward.

The maxim *actor sequitur forum rei* appears repeatedly in jurisdictional and conflict-of-laws discussions in historical sources. Understanding it requires recognizing that *actor* there means plaintiff, not performer or agent.

For researchers using the Law Mind Encyclopedia, the Section 1983 entry covers state actor doctrine as a distinct constitutional framework. The sovereign immunity entry addresses how government actors may be shielded from prosecution or suit even when their conduct would otherwise give rise to liability.

---

Historical Dictionary Support

The historical dictionaries agree on the core civil law meanings. Burrill is the most precise, citing the Institutes directly for the plaintiff sense and the Code for the forum maxim. Black's (both editions) supplements Burrill's account with the agent/steward meaning, noting the Roman practice of appointing slaves as business managers — a usage that has no survival in modern legal practice but is historically significant for understanding Roman commercial law.

Anderson is the most concise, leading with "a doer; a plaintiff" and moving quickly to the forum maxim. His treatment of personal actions and collisions between vessels under the forum discussion is a useful practical gloss not found in the other sources.

None of the historical dictionaries addresses the modern constitutional usage of *actor* (as in "state actor" or "government actor"). This is expected — that usage postdates all of them — but researchers should note the absence. The historical definitions are not wrong; they are simply incomplete for modern constitutional research purposes.

Webster's 1913 is the only source that openly lists both the legal and theatrical senses side by side, making it useful for confirming that the shift in common usage was already underway by the early 20th century.

---

Jurisdictional Note

The plaintiff sense of *actor* is operative in civil law jurisdictions and in historical common law sources drawing on Roman procedure. In modern American and English common law practice, *actor* in the plaintiff sense is archaic and rarely appears in contemporary pleadings or opinions. The "state actor" and "government actor" usages are distinctly American constitutional law terms.

---

Encyclopedia Cross-Reference

Sovereign Immunity and Criminal Prosecution of Government Actors — Law Mind Criminal Law Encyclopedia
Section 1983 — Civil Rights Litigation Against State Actors — Law Mind Constitutional Law Encyclopedia

---

ACTORmain

Black's Law Dictionary • 1891

In Roman law. One who acted for another; one who attended to another's business; a manager or agent. A slave who attended to, transacted, or superintended his master's business or affairs, received and paid out moneys, and kept accounts. Bur- rill. A plaintiff or complainant. In a civil or private action the plaintiff was often called by the Romans "petitor;" in a public action (causa publica) he was called "accusator." The defendant was called "reus," both in private and public causes; this term, how- ever, according to Cicero, (De Orat. ii. 43,) might signify either party, as indeed we might conclude from the word itself. In a private action, the defendant was often called "adversarius," but either party might be called so. Also, the term is used of a party who, for the time being, sustains the burden of proof, or has the initiative in the suit. In old European law. A proctor, ad- vocate, or pleader; one who acted for another in legal matters; one who represented a party and managed his cause. An attorney, bail- iff, or steward; one who managed or acted for another. The Scotch "doer" is the literal translation.

ACTORmain

Black's Law Dictionary • 1891

Actor qui contra regulam quid ad- duxit, non est audiendus. A plaintiff is not to be heard who has advanced anything against authority, (or against the rule.) Actor sequitur forum rei. According as rei is intended as the genitive of res, a thing, or reus, a defendant, this phrase means: The plaintiff follows the forum of the property in suit, or the forum of the de- fendant's residence. Branch, Max. 4. Actore non probante reus absolvitur. When the plaintiff does not prove his case the defendant is acquitted. Hob. 103. The Actori incumbit onus probandi. burden of proof rests on the plaintiff, (or on the party who advances a proposition affirma- tively.) Hob. 103.

ACTORmain

Burrill's Law Dictionary • 1867

Lat. [from agere, to act, to do, to move.] In the civil and common law. The party who institutes or prosecutes an action, (qui lege agit ;) a plaintiff, (querens.) Inst. 4. 6. 30, 34, 38. Id. 4. 15. 7. 9 a. Actor sequitur forum rei. The plaintiff follows the court of the defendant, (reus ;) that is, he must sue in the court of the place where the defendant resides. Cod. 3. 19. 3. Id. 3. 13. 2. 5. This was a maxim in the time of Bracton. Verum est quod sive laicum sive clericum velit quis convenire, debet adire judicem et sequi forum rei, et judicem habebit illum apud quem reus habet domicilium, sive domicilium habuerit sub jurisdictione unius vel duorum. It is true that whether one desires to sue a layman, or a clerk, he must apply to the judge, and follow the court of the defendant, and must have him as his judge with whom the defendant has his domicile, whether he has his domicile under the jurisdiction of one or two. Bract. fol. 401 a. But this maxim was not of universal application. Id. ibid. See Fleta, lib. 6, c. 37. The apparently exact verbal similarity between this and the preceding maxim will not escape notice; the difference consisting in the circumstance that the word rei in the one, is the genitive of res, (a thing,) and in the other, of reus, (a defendant.) Actore non probante absolvitur reus. The plaintiff not proving [his demand] the defendant is acquitted. Hob. 103. Actori incumbit probatio, [onus probandi.] The burden of proof lies on the plaintiff. Hob. 103 a. Lat. [from agere, to do, to act.] In the Roman law. One who acted for another; one who attended to another's business; a manager or agent. A slave who attended to, transacted or superintended his master's business or affairs, received and paid out moneys, and kept accounts, (rationes.) Dig. 10. 2. 8. Id. 11. 3. 1. 5. Id. 34. 1. 18. 3. Id. 34. 3. 12. Id. 40. 4. 53. Id. 40. 4. 59. pr. Bract. fol. 106 a. 376 a. 2 Bl. Com. 25. Sometimes termed agens, and pars actrix, (qq. v.) Inst. 4. 6. 33. Reg. Orig. Fleta, lib. 2, c. 63, § 11. In some cases, both parties are regarded as actors; (uterque actor est ;) and such actions are termed in the civil law, judicia duplicia, and mixtæ actiones; double or mixed actions. Dig. 44. 7. 37. 1. 1 Mackeld. Civ. Law, 188, § 193. Of this description is the modern action of replevin. But the term actor, even in these cases, properly belongs to the party commencing the proceedings, (ille actor qui primo provocaverit ad judicium.) Bract. fol. 102 b. 372 a. Eum Id. 40. 7. 40. 3. Id. 48. 5. 17. 5. Called actorem qui ad judicium provocasset. Dig. in Greek paypárturns. Dig. 40. 5. 41. 4. Distinguished from procurator. Cod. 5. 61. The manager, agent or attorney of a municipal or other corporation. Dig. 2. 4. 10. 4. Id. 3. 4. 1. 1. Id. 3. 3. 74. Id. Id. 36. 1. 27. Id. 36. 4. Id. 44. 2. 11. 7. Id. Calv. Lex. 5. 1. 13. Actor sequitur forum rei. The plaintiff follows the forum of the thing [in controversy.] He must sue in the court where the property is; that is, in the court of the place, or country, where the thing (res) in controversy is situate, (sita est ;) or, as it is 13. 5. 5. 7, 9. 12. Id. 37. 1. 3. 4. 50. 12. 8. A syndic. Id. 40. 5. 41. 4.

ACTORn.

Websters Unabridged Dictionary (1913) • 1913

One who acts, or takes part in any affair; a doer. A theatrical performer; a stageplayer. After a well graced actor leaves the stage. Shak. An advocate or proctor in civil courts or causes. Jacobs. One who institutes a suit; plaintiff or complainant.

actornoun

Wiktionary (English) • 2026

Wiktionary contributors • CC BY-SA 4.0 • via Kaikki
Extracted and formatted for display by Law Mind. Source link opens the current Wiktionary page and its contributor history; it is not a frozen copy of this extract.

Someone who institutes a legal suit; a plaintiff or complainant. | Someone acting on behalf of someone else; a guardian. | Someone or something that takes part in some action; a doer, an agent. | A person who acts a part in a theatrical play or (later) in film or television; a dramatic performer. | An advocate or proctor in civil courts or causes. | The subject performing the action of a verb. | The entity that performs a role (in use case analysis).

Explore the full Law Mind legal research platform.

Subscribe Encyclopedia Sign In