Polysemy—the existence of multiple related meanings for the same word or phrase—is a frequent phenomenon in legal and lay language. Although polysemy sometimes arises by accident, it also can be strategic: framers of legal rules can advance private and public interests by assigning meanings to terms that are different from—though connected to—the meanings that those terms carry outside the law. Understanding the functions of polysemy can help us design more effective legal rules and can shed light on ways in which legal actors translate language into power.

This Article undertakes a comprehensive analysis of polysemy’s origins, uses, and consequences across legal fields. It compares polysemy to monosemy, which arises when a word or phrase has the same meaning in legal and nonlegal language, and homonymy, which arises when a word or phrase has entirely different meanings in and outside law. It also identifies and examines a fourth category: “legalogisms,” or legal terms (like “res ipsa loquitur” and “Roth IRA”) that have no colloquial correspondent. The Article goes on to identify circumstances in which polysemy is and isn’t likely to be an effective rhetorical strategy for the law. Polysemy can increase communicative efficiency, reduce decision costs, and enhance law’s expressive effects. But polysemy also can confuse laypeople, mislead legal decisionmakers, and undermine law’s perceived legitimacy. And even when deployed effectively, polysemy can raise entry barriers to legal interpretation, impose negative externalities on adjacent legal systems, and redistribute wealth and status in ways that disproportionately benefit members of the legal profession.