Definition
In common law pleading, to rejoin means for a defendant to answer the plaintiff's replication with a pleading of fact. The rejoinder is the defendant's response at the third stage of the formal pleading exchange, following the declaration (plaintiff), the plea (defendant), and the replication (plaintiff's answer to the plea). To rejoin, therefore, is to produce that third-stage responsive pleading.
The term carries a secondary modern usage in patent law: to rejoin a patent claim means to re-insert a previously restricted or withdrawn claim into active examination, typically after allowance of the application, pursuant to USPTO rejoinder practice.
Common Language
Modern common usage (Wiktionary): To join again after separation; to re-enter the company of someone or something; also, to state something in reply.
Historical common usage (Webster's 1913): "To join again; to unite after separation. To come, or go, again into the presence of; to join the company of again. To state in reply."
The common meaning of rejoin — simply to re-enter, reunite, or retort — is superficially close to the legal pleading meaning but misses the structural significance entirely. In law, to rejoin is not merely to reply; it is to perform a specific, formally required act at a defined stage of the pleading sequence. A researcher who reads the term in a historical case or pleading record and interprets it as a general synonym for "respond" will misread the procedural posture of the litigation.
Common Confusion
REJOIN vs. REPLY vs. PLEAD: In common law pleading, each responsive act has a distinct name tied to its position in the sequence. The plaintiff replies (replication); the defendant rejoins (rejoinder); the plaintiff then surrejoins (surrejoinder); the defendant rebutts (rebutter); and so on. Treating these terms interchangeably obscures the stage of proceedings being described. Historical sources and older cases use these terms with precision that modern readers often flatten into a generic sense of "responding."
REJOINDER (noun) vs. REJOIN (verb): These are directly related — to rejoin is to file a rejoinder — but older sources sometimes use rejoinder loosely to describe any counter-reply, which can mislead. Verify context when the noun appears in a historical document.
Why It Matters in Research
The formal common law pleading system that gave rejoin its technical meaning was substantially abolished in most American jurisdictions by the adoption of code pleading in the mid-nineteenth century and later by the Federal Rules of Civil Procedure in 1938. As a result, rejoin in its pleading sense is almost exclusively a term of historical or English law research. Researchers working with pre-code American cases, English common law authorities, or equity pleading materials will encounter it regularly; those working with modern federal or state civil practice will not, except in historical analysis.
The trap in historical sources is sequence-mapping: to understand what it means that a defendant "rejoined," a researcher must reconstruct whether a replication had in fact been filed, because the act of rejoining presupposes that step. If the record skips the replication or uses informal language, the procedural posture can be difficult to reconstruct.
Anderson's note on "rejoining gratis" is a useful navigational signal: this phrase appears in older practice materials to describe a defendant who rejoins without compelling the plaintiff to obtain a rule of court first — a procedural courtesy that could affect the timeline and formalities of the pleading sequence. The phrase is rare and likely to be opaque without this context.
The patent law usage is entirely separate and modern. Researchers in USPTO prosecution history should treat "rejoin" and "rejoinder" in that context as terms of art governed by USPTO rules and examination guidelines, not by common law pleading doctrine.
Historical Dictionary Support
Black's Law Dictionary (both the first and second editions) and Burrill's Law Dictionary define rejoin identically: to answer a plaintiff's replication in an action at law by some matter of fact. The emphasis on "matter of fact" is significant — the rejoinder was required to be factual, not a pure legal argument, reflecting the common law pleading structure in which demurrers (raising points of law) and traverses or confessions-and-avoidances (raising matters of fact) were procedurally distinct instruments.
Anderson's Dictionary adds the phrase "rejoining gratis," cross-referencing JOINDER. This cross-reference is substantively useful: it signals that the act of rejoining was understood as a form of joinder in the pleading sequence, tying the term's etymology to its function within that sequence.
Burrill's entry contains a textual corruption in the available source — a passage about rehabilitation of witnesses in Scotland appears to have been merged into the rejoinder definition by a scanning or transcription error. Researchers relying on digitized versions of Burrill should be alert to this artifact; the authentic rejoinder definition aligns with Black's and Anderson's.
The historical dictionaries collectively do not address the patent law usage, which postdates all four sources. They also do not address the abolition of formal common law pleading, so they present the term in a context that no longer reflects active American procedural practice.
Jurisdictional Note
In English law and in American jurisdictions that retained common law pleading forms longest (certain equity courts, some state practice before code adoption), rejoin retained its formal technical meaning well into the nineteenth century. Modern American civil procedure has no equivalent pleading stage. Patent law rejoinder practice is federal and governed exclusively by USPTO rules and examination guidelines.