Definition
A separate action is a lawsuit brought by one party alone, for that party's own claims, when multiple parties share a common interest in the same transaction or occurrence but are legally unable—or choose not—to join together in a single suit. The term operates in contrast to a joint action, where multiple plaintiffs or defendants proceed together in one proceeding.
The concept arises in two distinct contexts:
1. Mandatory separation: When parties who would otherwise prefer to join cannot do so because joinder is legally unavailable—whether due to procedural rules, the nature of the claims, or defects in the capacity to sue jointly—each must bring a separate action asserting only their own rights.
2. Elective separation: When parties who could theoretically join choose instead to proceed individually, each maintaining a distinct lawsuit on their own behalf.
In both contexts, the defining feature is that the action belongs to one plaintiff and proceeds on that plaintiff's interests alone, even if parallel actions on related facts are pending elsewhere.
Common Confusion
"Separate action" is sometimes confused with severance. Severance occurs when a court splits claims or parties out of an already-filed joint action into distinct proceedings. A separate action, by contrast, is filed independently from the outset—it is never part of a joint proceeding to begin with. The distinction matters when analyzing filing deadlines, preclusion, and the sequence of procedural history.
The term also occasionally appears in family law contexts with a different emphasis. A "separate action" for divorce or legal separation simply refers to the distinct nature of the proceeding from other civil litigation, not to the joinder/severance dynamic that gives the term its primary technical meaning.
Why It Matters in Research
The primary research utility of this term is as a procedural marker in joinder analysis. When you encounter "separate action" in historical sources, the term is almost always doing one of two jobs: (1) describing the procedural consequence of a failed or unavailable joinder, or (2) distinguishing one party's individual suit from a co-party's parallel proceeding arising from the same facts.
Trap for researchers in historical sources: Before the merger of law and equity under the Federal Rules and their state equivalents, joinder rules were significantly narrower. A "separate action" in a 19th-century opinion frequently signals a mandatory procedural posture—the parties had no choice but to sue separately—whereas in modern sources the same phrase often reflects a strategic or discretionary choice. Do not assume that historical language about separate actions implies the same degree of procedural compulsion that it once did.
Cross-jurisdictional variation matters here. Some states retain more restrictive joinder rules than the federal model, making mandatory separate actions more common in those jurisdictions than a purely federal-practice lens would suggest.
When researching preclusion issues (res judicata, collateral estoppel), the existence of a separate action rather than a consolidated or joint proceeding can affect whether a judgment in one case binds parties in the parallel case. This is a recurring trap: litigants who bring separate actions on related claims may inadvertently create preclusion exposure if one action concludes before the other.
The term connects naturally to class action analysis. Where a class has not been certified, putative class members bringing individual suits are, by definition, maintaining separate actions—and courts discussing the relative efficiency of class treatment versus separate actions use the term in exactly this sense.
Historical Dictionary Support
Black's and Bouvier's are in close agreement on the core meaning: a separate action is the procedural vehicle available to each of several persons when they share a common grievance but cannot proceed jointly. Both sources frame the term reactively—as the consequence of unavailable joinder—rather than as a freestanding concept with its own affirmative content.
Black's formulation is slightly broader, acknowledging that parties "concerned in the same transaction" may bring separate actions even when they might have preferred to join. Bouvier's is more compact, treating the separate action essentially as the residual category left when joinder is denied.
Neither historical source addresses the modern context in which parties may strategically elect separate actions despite available joinder, nor do they engage with the procedural complexity introduced by compulsory joinder rules, class actions, or multidistrict litigation—all of which significantly shape how the term functions in contemporary research. Researchers working in modern procedural contexts should treat the historical definitions as capturing the term's origin logic rather than its full present-day scope.
Jurisdictional Note
Federal practice under Rule 20 of the Federal Rules of Civil Procedure permits permissive joinder broadly, meaning that separate actions in federal court are more often a matter of election than compulsion. State courts with more restrictive joinder rules—particularly those that have not fully adopted the federal model—may more frequently generate mandatory separate actions as a procedural outcome.
Encyclopedia Cross-Reference
Family Law Encyclopedia: Divorce — Legal Separation (Distinguished from Divorce) [family_52] — relevant when "separate action" appears in domestic relations contexts where it describes a standalone legal separation proceeding distinct from divorce.