Definition
The legal condition of being married to only one person at a time. Monogamy is the foundational marital structure recognized by the common law and codified throughout American and English statutory law — it is not merely a preferred arrangement but the exclusive legal form of valid marriage. A person who contracts a second marriage while a prior valid marriage remains undissolved commits bigamy, a criminal offense in every American jurisdiction. Monogamy, in legal usage, describes both the act of marrying one person and the ongoing status of having only one living, undivorced spouse.
Common Language
Modern common usage (Wiktionary): A form of sexual bonding involving a permanent pair bond between two beings; the practice of being married to one person as opposed to multiple.
Historical common usage (Webster's 1913): Single marriage; marriage with but one person, husband or wife, at the same time, opposed to polygamy; also, one marriage only during life, opposed to deuterogamy.
The common usage of monogamy has expanded in contemporary culture to encompass romantic or sexual exclusivity outside of legal marriage. The legal definition is narrower and more precise: it concerns the civil status of marriage only. A person may be monogamous in the popular sense while legally single, widowed, or divorced; the law cares only whether a valid marriage to one person subsists at a given time. Webster's 1913 captures an older theological overlay — contrasting monogamy with deuterogamy (second marriage after a spouse's death) — that has no independent standing in modern secular law.
Common Confusion
Monogamy is sometimes conflated with related but legally distinct concepts. Monogamy describes lawful marital status (one spouse, currently). Bigamy describes the criminal act of contracting a second marriage without dissolving the first. Polygamy describes a system in which multiple simultaneous marriages are contracted or practiced, whether or not criminalized in a given jurisdiction. The distinctions matter: monogamy is a status, bigamy is an offense, and polygamy is a marital structure. Historical sources occasionally used monogamy as simply the antonym of polygamy or bigamy without defining its independent legal content, which can create confusion when reading older treatises.
Why It Matters in Research
Monogamy functions in legal research less as a term requiring independent analysis and more as a structural premise underlying marriage law across the common law tradition. Researchers encounter the term primarily in three contexts:
First, in criminal law sources, where monogamy appears as the baseline against which bigamy and polygamy statutes are defined. The historical dictionaries derive their definitions partly from opposition — monogamy is what bigamy violates. This means the legal content of monogamy has often been elaborated through bigamy prosecutions rather than in standalone doctrine.
Second, in constitutional and family law debates, particularly those arising from the nineteenth-century federal conflicts with Mormon polygamous practice. Cases from this period, and the federal statutes targeting polygamy in the territories, produced some of the most legally substantive discussions of what monogamy requires as a matter of public policy and civil order. Researchers working in this area should expect that the strongest doctrinal statements about monogamy appear in anti-polygamy cases and legislation, not in pro-monogamy affirmative doctrine.
Third, in the modern marriage equality context. The redefinition of civil marriage to include same-sex couples did not alter the monogamy requirement — same-sex marriage law retained the one-spouse-at-a-time structure. Researchers should be careful not to conflate debates about who may marry with debates about how many may marry simultaneously; the legal literature treats these as separate questions.
Historical sources use the term with a consistent but noticeably male-centered framing. Both Black's editions define monogamy as the marriage of "one wife only" or restraint "to a single wife," reflecting the historical legal position of marriage as a status defined primarily from the husband's perspective. Bouvier corrects this somewhat by defining monogamy as having only one husband or one wife at a time. Researchers reading nineteenth-century sources should note this asymmetry and not mistake it for a substantive legal distinction.
Historical Dictionary Support
Black's Law Dictionary (both editions) and Bouvier's Law Dictionary are in substantial agreement, all three tracing their core definition to Wolff's Droit de la Nature (§ 857), a natural law treatise. This shared sourcing means the historical dictionaries are not independently corroborating one another — they are drawing from the same origin. The practical definitions they offer are functionally identical: a marriage between one man and one woman to the exclusion of all others.
The notable divergence is Bouvier's gender-neutral framing ("only one husband or one wife"), which stands in contrast to Black's husband-centered language. Neither edition of Black's acknowledges the wife's parallel legal position in the definition itself, though the substantive law of bigamy applied to both sexes.
All three sources treat monogamy as an essentially self-defining term — its legal content comes from contrast with bigamy and polygamy rather than from positive doctrinal development. This limits the utility of the historical dictionary entries for any research question more nuanced than basic terminology.
Jurisdictional Note
Monogamy as a legal requirement applies uniformly across all U.S. jurisdictions and throughout the common law tradition in England and its former colonies. The one-spouse requirement is embedded in every state's marriage statute and is a condition for the validity of marriage recognized in conflict-of-laws analysis. Polygamous marriages contracted abroad are generally not recognized as valid in the United States, though specific recognition questions in immigration and inheritance contexts remain areas of active legal development.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Marriage; Bigamy; Polygamy