Definition
A word of ambiguous scope used in legal instruments, statutes, and pleadings. Its meaning shifts depending on context:
(1) Disjunctive sense: "One or the other" of two (or occasionally more) specified things. This is the word's primary legal meaning — presenting alternatives without requiring both.
(2) Conjunctive/distributive sense: "Each" of two things, equivalent to "both." Courts have recognized this usage when context demands it, as where a statute or contract imposes an obligation that must apply to each of two items separately rather than to a single selection from among them.
(3) Statutory sense: Occasionally construed to mean "any" when used in a statute where the legislature plainly intended to cast the widest net among a class of options.
The determinative question in any disputed usage is whether the instrument's context calls for a disjunctive reading (one or the other, but not necessarily both) or a distributive reading (each, separately). Courts will look to surrounding text, the evident purpose of the provision, and the consequences of each reading.
Common Language
Modern common usage (Wiktionary): "One or the other of two people or things"; also, "both, each of two or more."
Historical common usage (Webster's 1913): "One of two; the one or the other — properly used of two things, but sometimes of a larger number, for any one."
The ordinary English word already carries both the disjunctive and conjunctive possibilities, so the legal ambiguity is not unique to law. What matters for researchers is that courts do not treat the colloquial ambiguity as a reason to default to any single meaning — they require a context-specific analysis, and the stakes of that analysis in contract interpretation, statutory construction, and pleading are consequential. The common meaning provides no safe harbor.
Common Confusion
EITHER vs. OR: "Either...or" constructions are frequently analyzed together, but they are not the same question. "Or" carries its own disjunctive/conjunctive ambiguity in legal drafting. A court resolving an "either...or" clause must construe both words, and the analysis of "either" may not track the analysis of "or" in the same instrument. See OR for separate treatment.
EITHER vs. ANY: When "either" is used in a statute to mean "any," it is not simply a synonym — it signals that the drafter was thinking of a defined universe of alternatives. Courts have been cautious about extending an "any" reading beyond clear statutory context.
Why It Matters in Research
The practical hazard in researching "either" is that its meaning has been resolved differently across jurisdictions, instruments, and time periods — and historical sources often treat the ambiguity as settled when it is not.
Historical cases resolving the disjunctive/conjunctive question are highly fact-specific. A holding that "either" means "each" in a railroad franchise statute from 1880 is weak authority for its meaning in a modern commercial contract. Researchers should not assume a single canonical meaning and should instead trace how the specific jurisdiction has treated the word in the specific type of instrument at issue.
In statutory construction, the move from "one or the other" to "any" is particularly significant. If a penalty statute uses "either" and a court reads it as "any," the scope of liability can expand substantially. Look for legislative history or surrounding statutory language that confirms the broader reading before relying on it.
In pleading and jury instruction research, "either" can create genuine issues of verdict ambiguity. A general verdict on a multi-count complaint using "either" charges may not reveal which theory the jury credited. This has implications for appellate review and issue preclusion.
Corpus researchers should note that historical legal writers sometimes used "either" where modern drafters would use "each" or "any" as a matter of stylistic habit, not legal precision. Treating every instance of "either" in a historical instrument as a deliberate disjunctive choice overstates the intentionality of period drafting conventions.
Historical Dictionary Support
The historical dictionaries consulted are in basic agreement on the core point: "either" is not limited to its strict disjunctive sense and may carry the meaning of "each." Black's (1st and 2nd editions) and Bouvier's all cite the same Illinois authority for the "each" reading. Anderson extends the analysis usefully by flagging the "any" reading in statutory context and noting that "sometimes" the word means "one and the other" — a formulation that aligns with conjunctive use without fully committing to it.
What the historical dictionaries do not address is the analytical framework for choosing among the competing meanings. They record that the word is flexible; they offer no guidance on when to apply which sense. The brief entries reflect the courts' own reluctance to fix the word's meaning in advance of context.
The absence of a definitive historical treatment is itself informative: by the late nineteenth century, courts and commentators recognized the ambiguity as real and recurring but addressed it case by case rather than through a canonical rule. Researchers should not expect the historical sources to resolve the question — they confirm the problem without solving it.
Jurisdictional Note
No jurisdiction appears to have adopted a fixed default rule that "either" always means one thing. The interpretive approach — looking to context, purpose, and consequences — is consistent across American jurisdictions, though the specific results vary. Researchers working in a particular state should check whether local statutory construction rules or pattern jury instructions have assigned a default meaning in specific contexts.