Definition
A dictionary, in legal usage, carries two distinct meanings:
1. A reference work arranging words alphabetically with explanations of their meanings, used by courts and counsel to establish the ordinary or plain meaning of undefined statutory and contractual terms.
2. The "dictionary clause" (or "definition section") of a statute — the provision within a legislative enactment that defines key terms as they are to be understood throughout that statute. Courts treat these definitions as authoritative and binding within the statute's scope, displacing any ordinary or specialized meaning the same word might carry elsewhere.
Common Language
Modern common usage (Wiktionary): To look up in a dictionary; to add to a dictionary; to compile a dictionary. The noun sense — a book of words with definitions — is well established in ordinary English.
Historical common usage (Webster's 1913): "A book containing the words of a language, arranged alphabetically, with explanations of their meanings; a lexicon; a vocabulary; a wordbook."
The common-language sense treats a dictionary as an authoritative source for word meanings. Legal usage cuts against this in a critical respect: courts do not treat published dictionaries as controlling. Where a word has received a settled legal construction or reflects uniform custom, a dictionary definition that conflicts with that construction is disregarded. The dictionary is a starting point for ordinary meaning, not a trump card.
Common Confusion
Two distinct things travel under this label and are frequently conflated. The first is the external reference work (Black's Law Dictionary, Merriam-Webster, Oxford English Dictionary) consulted by courts when determining the plain meaning of statutory text. The second is the internal dictionary clause — the definition section built into the statute itself. These operate differently: an external dictionary is persuasive evidence of ordinary meaning; an internal dictionary clause is part of the statute and legally binding within its domain. Researchers who treat these as the same instrument will misread both the interpretive argument and the statutory structure.
Why It Matters in Research
The legal significance of "dictionary" sits almost entirely in statutory and contractual interpretation. Two research traps are worth flagging:
First, the weight given to external dictionaries has shifted over time and varies by court. Textualist judges in the modern era cite dictionaries with greater frequency and authority than their predecessors. Researchers working with older materials should not assume that a court's failure to cite a dictionary reflects interpretive error — it may simply reflect the interpretive conventions of that era, when legislative history carried more weight.
Second, the dictionary clause of a statute deserves early attention. When a term appears in statutory text, the first search should be the statute's own definition section, not an external reference work. A statute's internal definition frequently diverges from ordinary meaning, and courts are bound by it. Anderson's note that "no meaning of a word, which has received a construction by law or uniform custom, can be adopted from the dictionaries in conflict with that construction" remains a reliable statement of this principle. Missing the definition clause and relying on an external dictionary instead is a common and consequential error.
Third, in contract interpretation, courts sometimes distinguish between technical trade meaning, legal meaning, and dictionary meaning. A word in a commercial contract may carry none of the same content as the same word in a general dictionary. Corpus research on contract disputes should flag all three registers.
Historical Dictionary Support
Anderson's Dictionary of Law cross-references DEFINITION and WORD, treating the "dictionary" entry primarily as a doctrinal rule about the limits of lexicographic authority. The formulation is careful: dictionaries may not be used to override a construction settled by law or custom, but where no such settled construction exists and a word's usage is reconcilable with established meaning, a dictionary definition cannot unilaterally displace it either. The entry also introduces the "dictionary clause" as the statute's own definitional section — a usage that remains current.
What Anderson's does not address, reflecting the limits of its era, is the contested role of dictionaries in modern textualism. The twentieth century saw significant debate about whether courts should prefer dictionaries that were contemporary with a statute's enactment versus current editions, and whether different dictionary types (general, legal, specialized technical) carry different weight for different kinds of statutory language. These questions are largely absent from historical dictionary sources and must be sourced elsewhere.
Jurisdictional Note
Federal courts and most state courts follow the general principle that external dictionaries are persuasive, not binding, on questions of plain meaning. Some state courts have adopted local rules or interpretive canons that expressly address when dictionary evidence is admissible in statutory construction arguments. Researchers should not assume uniform practice across jurisdictions.
Encyclopedia Cross-Reference
Law Mind Encyclopedia — Statutory Interpretation
Law Mind Encyclopedia — Legal Language and Construction
Law Mind Encyclopedia — Contracts: Interpretation and Construction