What Fornication Means: Everyday, Legal and Biblical Definitions

What is the dictionary definition of fornication?

Fornication is, in the standard American dictionary definition, "consensual sexual intercourse between two persons not married to each other" ^[1]. Merriam-Webster uses the same wording in its medical entry and sends readers to compare the word with adultery ^[1]. The definition rests on three elements: sexual intercourse, the consent of both people, and the absence of a marriage between them.

Each element does work. Building consent into the definition places nonconsensual acts outside the word, since those are named by other terms in both law and ordinary speech. The marriage test looks at the relationship between the two partners, and Merriam-Webster's usage note draws the practical consequence: adultery applies only when at least one participant is married, whereas fornication describes consensual sex between unmarried people ^[1].

Etymonline adds a historical nuance. In the strict sense the word meant consensual sex between two unmarried people, but the Bible extended it to adultery ^[2]. Merriam-Webster dates the first known use to the 14th century and traces the word through Middle English and Anglo-French to Late Latin, and ultimately to a verb meaning to consort with prostitutes ^[1]. Etymonline places the first English record around 1300 ^[2].

The modern definition is neutral in a way the word's history is not. A dictionary describes the act without saying whether it is wrong, yet the word entered English through church writing and Bible translation. Much of its present tone comes from that origin, which is traced in our article on the etymology of fornication.

The main senses of "fornication" in American usage

Sense	Source	Who is covered	Example or penalty
Dictionary	Merriam-Webster	Two consenting people not married to each other	First known use: 14th century
State law	Georgia, O.C.G.A. § 16-6-18 (2025 code)	An unmarried person who voluntarily has intercourse with another person	Punished as a misdemeanor
State law	South Carolina Code § 16-15-80	A man and a woman, both unmarried, who live together or have habitual intercourse	Fine of $100 to $500 and/or 6 months to 1 year (§ 16-15-60)
State law	Illinois, 720 ILCS 5/11-40	Anyone who has open and notorious intercourse with a person other than his or her spouse	Class B misdemeanor
Church teaching	Catechism of the Catholic Church, § 2353	An unmarried man and an unmarried woman	Placed in the section on the vocation to chastity
Bible (King James Version)	Greek porneia, 26 occurrences in the Textus Receptus	Illicit sexual intercourse in general, at times including adultery; figuratively idolatry	1 Corinthians 6:18, "Flee fornication"

How do US laws define fornication?

In the United States, fornication is a matter of state law, so each state that punished it wrote its own definition. Cornell Law School's Wex legal dictionary gives the common core: fornication occurs when two unmarried individuals have sexual intercourse, and the conduct is now more commonly called premarital sex ^[3]. Wex adds that a few states still have fornication laws on the books, but that they generally cannot be enforced since Lawrence v. Texas (2003), which held that private sexual conduct is protected by the Due Process Clause of the Fourteenth Amendment ^[3].

The statutes that remain show how much the legal meaning can vary. Georgia's is the closest to the dictionary: an unmarried person commits fornication by voluntarily having intercourse with another person, and is punished as for a misdemeanor ^[4]. The 2025 edition of the Georgia code traces the section's history back to laws of 1833 and to its re-enactment in the 1968 criminal code ^[4]. The text looks only at the status of the person charged, not at that of the partner.

South Carolina is narrower. Its code defines fornication as living together with sexual intercourse, or habitual intercourse without living together, between a man and a woman who are both unmarried ^[5]. A single encounter therefore falls outside the text. The penalty, shared with adultery, is a fine of $100 to $500, six months to a year in prison, or both, and the section's history goes back to an act of 1880 ^[5].

Illinois takes yet another route. Its statute, in force in its current form since July 1, 2011, covers a person who knowingly has intercourse with someone other than his or her spouse, but only if the behavior is open and notorious, and makes it a Class B misdemeanor ^[6]. Under that wording a married person can commit fornication, which the dictionary sense excludes, while private conduct is not covered at all.

Older statutes sometimes turned on the woman's status. Minnesota's law, as quoted in a 2022 report of the state House, applied when any man and a single woman had intercourse ^[7]. Merriam-Webster's legal definition keeps a trace of that tradition by describing intercourse between a man and especially a single woman ^[1]. Minnesota's code now shows the section repealed by the 2023 session laws ^[8]. The current list of statutes and recent repeals is set out in our overview of fornication laws still on the books.

What does fornication mean in the Bible?

In the King James Version, "fornication" is the regular English rendering of the Greek noun porneia. The Blue Letter Bible concordance, keyed to the Textus Receptus that the 1611 translators used, counts 26 occurrences of porneia, and the KJV translates every one of them as fornication ^[9]. The lexicon outline gives a wide meaning: illicit sexual intercourse, including adultery and unions with close relatives, and metaphorically the worship of idols ^[9].

The biblical word is therefore broader than the dictionary one. Thayer's Greek lexicon, reproduced on the same page, notes that porneia refers to adultery in Matthew 5:32 and 19:9, yet is listed separately from moicheia, the Greek word for adultery, in Matthew 15:19, Mark 7:21 and Galatians 5:19 ^[9]. Readers of the KJV thus meet fornication both as a general name for sexual sin and as a companion of adultery in lists of vices.

Several verses are often cited in American churches. The shortest is 1 Corinthians 6:18, rendered "Flee fornication" in the KJV ^[10]. In 1 Corinthians 7:2, the KJV presents marriage as a way to avoid fornication, and in the Book of Revelation the word takes the figurative sense that the lexicon describes as the worship of idols ^[9].

Modern translations often choose other words for the same Greek. In 1 Corinthians 6:18, the New International Version and the English Standard Version say "Flee from sexual immorality," the New Living Translation speaks of sexual sin, and the New Revised Standard Version of 1989 kept "Shun fornication!" ^[10].

Church teaching can be narrower than the Bible. The Catechism of the Catholic Church defines the term in paragraph 2353: "Fornication is carnal union between an unmarried man and an unmarried woman" ^[11]. The paragraph sits in the section on the vocation to chastity, and its definition, limited to two unmarried people, matches the dictionary rather than the wider Greek word ^[11].

Is fornication the same as premarital sex?

In everyday American usage the two terms largely overlap, and Wex treats premarital sex as the current name for fornication ^[3]. The overlap is not complete. "Premarital" refers to a time before marriage, while the dictionary sense of fornication also covers people who are widowed, divorced or never marry ^[1].

The differences grow in other contexts. In the KJV, fornication can include adultery, which no one would call premarital ^[9]. In South Carolina's code it requires cohabitation or habitual intercourse ^[5], and in Illinois it can involve a married person ^[6]. The two phrases also differ in tone: "premarital sex" describes timing without passing judgment, while "fornication" names a category of sin or of crime.

Google Books data show how the vocabulary shifted in print. In the American English corpus, "premarital sex" barely registers before the 1940s; its frequency roughly tripled between 1960 and 1970 and reached its highest level in 2008 ^[12]. "Fornication" was most frequent in the early 19th century, at about 3.6 occurrences per million words around 1810, fell more than tenfold by 1940, and then rose again after 1980 to about 0.77 per million words in 2019 ^[12].

These curves measure printed books, not speech, and they do not show who used the words or why. They do confirm that "premarital sex" is a 20th-century coinage in common use, while "fornication" never disappeared from American print.

How is the word used today?

Today "fornication" lives mainly in three settings: religion, law and history writing. It is a formal word rather than slang, and neutral writing tends to prefer phrases such as "sex outside marriage" or "premarital sex." The example sentences that Merriam-Webster collects from recent media, published between 2023 and 2025, use it to discuss historical religious rules and to summarize television plots ^[1].

Its religious life owes much to the King James Version. The Bible in American Life study, produced by the Center for the Study of Religion and American Culture at IUPUI, found that 55 percent of Americans who reach for a Bible use the KJV, against 19 percent for the NIV, as Christianity Today reported in 2014 ^[13]. The same report cited an American Bible Society and Barna figure of 52 percent reading the KJV or the New King James Version ^[13]. With that readership, the word stays familiar from Scripture even though most recent translations have replaced it.

In law, the word now appears mainly in statute books and in news of repeals. Minnesota's 2023 repeal ^[8] is one recent example, and legal reference works such as Wex present the remaining statutes as largely unenforceable ^[3]. Where the word survives in a code, as in Georgia, South Carolina and Illinois, it is old drafting that, according to Wex, generally cannot be enforced against private conduct ^[3][4][5][6].

Which words belong to the same family?

The verb is fornicate, which Merriam-Webster defines as to commit fornication and dates to 1552 ^[14]. Its forms are fornicated, fornicating and fornicates ^[14]. The verb arrived in English roughly two and a half centuries after the noun.

The person is a fornicator, a noun Etymonline dates to the late 14th century, from the Late Latin agent noun fornicator ^[2]. English also tried feminine forms: fornicatrice around 1500, fornicatrix in the 1580s and fornicatress in the 1590s ^[2]. Merriam-Webster's current entries list only fornicator ^[14].

A more distant relative is fornix. English has used it since the 1680s for various arched formations, especially in anatomy, from a Latin word meaning arch or vaulted chamber ^[15]. The anatomical term shares the root of fornication but none of its moral meaning.

Frequently asked questions

Can married people commit fornication?

Under the usual dictionary definition, no: when one partner is married to someone else, the act is called adultery ^[1]. Some texts draw the line differently. Illinois's statute covers anyone who has open and notorious intercourse with a person other than his or her spouse ^[6], and Etymonline notes that the Bible extended fornication to adultery ^[2].

Is fornication a formal or old-fashioned word?

It is a formal word with a religious and legal history, not slang. It remains common in Bible study, law and history writing, while everyday speech usually prefers "premarital sex" or "sex outside marriage." Cornell's Wex notes that the conduct is now more commonly called premarital sex ^[3].

What is the verb form of fornication?

The verb is fornicate, with the forms fornicated, fornicating and fornicates. Merriam-Webster dates its first known use to 1552, long after the noun ^[14]. The person is called a fornicator.

What is the opposite of fornication?

There is no exact antonym. In religious usage the contrasting value is chastity: the Catholic Catechism defines fornication in its section on the vocation to chastity ^[11]. In secular terms, the contrasting ideas are abstinence or sex within marriage.

Is fornication illegal in the United States?

Only on paper, in a few states. Georgia, South Carolina and Illinois still list fornication offenses ^[4][5][6], but such laws generally cannot be enforced against private consensual conduct since Lawrence v. Texas in 2003 ^[3]. Minnesota repealed its law in 2023 ^[8].

Do modern Bibles still use the word fornication?

Some do, but many do not. In 1 Corinthians 6:18, the KJV and the 1989 New Revised Standard Version keep fornication, while the NIV and the ESV say sexual immorality and the New Living Translation speaks of sexual sin ^[10].

What is the difference between fornication and adultery?

Adultery requires at least one partner who is married to someone else; fornication describes consensual sex between people who are not married ^[1]. Some state codes, such as South Carolina's, define both offenses side by side with the same penalty ^[5]. The distinction is explained in detail in fornication vs adultery.