Definition
In iisdem terminis is a Latin maxim meaning "in the same terms." In legal usage, it describes a situation where a proposition, document, offer, agreement, or legal instrument is expressed or repeated in exactly the same words — without alteration, qualification, or variation. The phrase is used to assert that two statements, instruments, or provisions are identical in their language, and therefore identical in their legal effect.
Why It Matters in Research
This is a narrow but precise term of art. Researchers encounter it most commonly in older English and American case law when courts are comparing the exact wording of successive instruments, pleadings, statutes, or offers — particularly where the legal consequence turns on whether language was reproduced verbatim or subtly changed. A variation in terms, even slight, could defeat the claim that two instruments operated in iisdem terminis, with significant consequences for contract formation, estoppel arguments, or statutory construction.
The phrase appears with some frequency in early nineteenth-century English reports, and the single citation shared by all three historical dictionaries — 9 East, 487 — points to the King's Bench reports of Sir Edward East, a common reference point in American courts of the early republic through reception of English common law. Researchers using nineteenth-century American case law should note that this citation was treated as authoritative shorthand: courts citing it were often not elaborating on the underlying holding but using the phrase as a doctrinal marker to indicate terminological identity.
The term is essentially absent from modern legal writing, where the same concept is conveyed in plain English ("in identical terms," "verbatim," "in the same words"). Its appearance in a source therefore functions as a reliable period marker: it signals pre-twentieth-century drafting or argumentation. Researchers encountering it in historical documents should treat it as a signal to examine the surrounding context carefully — courts invoking the phrase were typically making a point about exact textual reproduction as a legal requirement, not a stylistic one.
There are no meaningful jurisdictional variations because the phrase is a Latinate term of art drawn from the English common law tradition and was never codified; it was simply adopted into the vocabulary of courts applying common law reasoning.
Historical Dictionary Support
Black's, Burrill's, and Bouvier's are in complete agreement — all three define the phrase identically as "In the same terms" and all three cite the same source, 9 East, 487. The uniformity is striking and itself informative: it suggests the phrase had a settled, uncontested meaning in the common law tradition and that no serious doctrinal dispute surrounded its definition. The historical dictionaries add no elaboration beyond the translation and citation, which reflects the term's status as a precisely bounded phrase rather than a contested legal concept.
What the historical dictionaries do not provide is any guidance on how the principle was applied — whether in contract formation disputes, statutory interpretation, or pleading practice. Researchers should not expect those sources to carry the analytical weight; the phrase is the dictionary entry, and its application must be recovered from the cases themselves.