Why Modern Bibles Say "Sexual Immorality" Instead of Fornication

What does the Greek word porneia mean?

Porneia is a Greek noun meaning illicit sexual intercourse in general, with a figurative sense of idolatry. The Blue Letter Bible lexicon lists, under its first sense, adultery, fornication, homosexual acts, intercourse with animals, unions with close relatives as defined in Leviticus 18, and intercourse with a divorced man or woman, citing Mark 10:11-12 ^[1]. Its second, metaphorical sense is the worship of idols ^[1].

Strong's dictionary gives a shorter gloss with the same breadth: harlotry, including adultery and incest, and figuratively idolatry ^[1]. The noun derives from the verb porneuō, "to commit fornication" ^[1]. In the Greek text used by the King James translators, porneia occurs 26 times ^[1]. In John 8:41 it even appears in a dispute about birth, when Jesus' opponents reply, in the KJV, "We be not born of fornication" ^[1].

Thayer's lexicon, reproduced on the same page, distinguishes two kinds of use. In some passages, such as Matthew 15:19, Mark 7:21 and Galatians 5:19, porneia stands next to moicheia, adultery, as a separate item in a list ^[1]. In others, such as Matthew 5:32 and 19:9 on divorce, it refers to adultery itself ^[1]. The word is therefore both broader than adultery and capable of including it.

The metaphorical sense is strongest in Revelation. Thayer cites Revelation 2:21 for the defilement of idolatry, linked to eating food sacrificed to idols, and explains it by the Old Testament image of God's covenant with Israel as a marriage ^[1].

Porneia in four key verses, from the KJV to recent translations

Verse	KJV (1611)	NRSV (1989)	NIV	ESV	CSB
1 Corinthians 6:18	Flee fornication	Shun fornication!	Flee from sexual immorality	Flee from sexual immorality	Flee sexual immorality!
1 Thessalonians 4:3	abstain from fornication	abstain from fornication	avoid sexual immorality	abstain from sexual immorality	keep away from sexual immorality
Matthew 5:32	saving for the cause of fornication	except on the ground of unchastity	except for sexual immorality	except on the ground of sexual immorality	except in a case of sexual immorality
Revelation 17:2	have committed fornication	have committed fornication	committed adultery	have committed sexual immorality	committed sexual immorality with her

How did the King James translators render it?

The King James translators rendered porneia the same way every time: all 26 occurrences in their Greek text appear as "fornication" ^[1]. The best-known example is the two-word command of 1 Corinthians 6:18, "Flee fornication" ^[3]. Others include the instruction of 1 Thessalonians 4:3 to "abstain from fornication" ^[10] and the requests that the Jerusalem council sends to gentile believers in Acts 15 ^[1]. The word also appears in the vice lists of Romans 1:29 and Galatians 5:19, where it stands beside wickedness, covetousness, uncleanness and lasciviousness ^[1].

That consistency had consequences for three centuries. Britannica notes that the King James Version, published in 1611 under James I, was generally accepted as the standard English Bible from the mid-17th to the early 20th century ^[2]. During that period, "fornication" was the English word through which most readers met the Greek concept.

In American churches the KJV's influence is still visible. The Bible in American Life study, produced at IUPUI and reported by Christianity Today in 2014, found that 55 percent of Americans who reach for a Bible use the KJV and 19 percent the New International Version ^[14]. The same article notes that the NIV had topped the bestseller list of Christian retailers for decades ^[14]. The two words therefore circulate side by side in American religious life. Online interest showed the same split: the 2014 article reported Bible searches on Google at about 45 percent for the KJV and 24 percent for the NIV ^[14].

The English word, meanwhile, narrowed. Merriam-Webster defines fornication today as consensual intercourse between two people who are not married to each other ^[16]. A modern reader of "Flee fornication" is likely to hear a rule about unmarried sex, while the Greek porneia covered adultery, incest and other unions as well ^[1].

Why do the NIV and ESV say sexual immorality?

The NIV and the ESV use "sexual immorality," a general English phrase for a general Greek word. Neither version contains "fornication" anywhere: BibleGateway keyword searches return no verse with the word in the NIV or in the ESV ^[4][5]. In 1 Corinthians 6:18 both read "Flee from sexual immorality" ^[3].

Their publishers describe different aims. The NIV's translators, an independent team of scholars from several denominations, say they balance transparency to the original with clarity of meaning and use global English as it is spoken today ^[6]. The publisher claims more than 650 million copies distributed and calls the NIV the most widely read Bible in contemporary English ^[6]. The ESV describes itself as an "essentially literal" translation in contemporary English, first published in 2001 ^[7]. Neither page discusses porneia specifically.

The gap between the definitions suggests why both versions converge. If fornication now means sex between unmarried people ^[16], it no longer covers everything the lexicons place under porneia ^[1]. "Sexual immorality" is wide enough to include adultery and incest, which keeps the Greek breadth, though it is also vaguer.

A similar argument has been made about another translation. Writing on the Enter the Bible site in June 2026, the Methodist minister Gerald C. Liu explains that the New Revised Standard Version of 1989 had already moved away from fornication as a reliable rendering of porneia, and that the 2021 NRSV Updated Edition changed about 25 instances of porneia and related forms ^[9]. He argues that porneia does not simply mean sex before marriage ^[9].

Does the change alter the meaning of the verses?

The change alters what a modern reader hears more than what the Greek says. A narrow English word can make a broad prohibition sound like a specific rule, and a broad English phrase can leave the reader unsure what is covered. Both renderings rest on the same Greek noun ^[1][3].

Scholars do not agree on how wide porneia was. Liu, drawing on the historian Kyle Harper, holds that the word first referred to specific practices in the Hellenistic world, that Paul stretched it to a range of illicit sexual practices, and that later preachers used it even more broadly ^[9]. Other readers stress the lexicon definitions, which already include fornication in the modern sense among the forms of porneia ^[1].

The clearest test case is Matthew 5:32, the exception clause on divorce. The KJV reads "saving for the cause of fornication," the NIV "except for sexual immorality," the NRSV "except on the ground of unchastity," the New Living Translation "unless she has been unfaithful," and the Catholic New American Bible "unless the marriage is unlawful" ^[12]. Each wording points toward a different interpretation, as discussed in our reading of Matthew 5:32.

Translation also shapes the figurative passages. In Revelation 17:2, where the verb and the noun describe idolatry through a sexual image, the KJV and the NRSV say "committed fornication," the ESV "committed sexual immorality," the NIV and the New Living Translation "committed adultery," the NASB "committed acts of sexual immorality," and the New American Bible speaks of "harlotry" ^[11]. Here the NIV chose the image of marital betrayal over the general term.

Which verses are most affected?

The verses most affected are the commands and lists that readers quote most often. 1 Corinthians 6:18 is the most visible: "Flee fornication" in the KJV and the American Standard Version, "Fly fornication" in the Douay-Rheims, "Flee from sexual immorality" in the NIV and the ESV, "Flee sexual immorality!" in the Christian Standard Bible, and "Run from sexual sin!" in the New Living Translation ^[3].

1 Thessalonians 4:3, a short statement on holiness, shows the same divide. The KJV, the NRSV and the Douay-Rheims say "abstain from fornication," the ESV and the NASB of 1995 "abstain from sexual immorality," the NIV "avoid sexual immorality," and the Catholic New American Bible "refrain from immorality" ^[10]. Young's Literal Translation stands apart with "abstain from the whoredom" ^[10].

Other passages follow the pattern. In 1 Corinthians 7:2, the KJV presents marriage as a way "to avoid fornication," and in Acts 15:20 and 15:29 the council asks gentile believers to abstain from it ^[1]. Related verses that use the noun pornos, rendered fornicator or whoremonger in the KJV, are compared in our article on fornicators and whoremongers.

The cumulative effect is visible in American print. In the Google Books corpus of American English, the phrase "sexual immorality" more than tripled in frequency between 1990 and 2010, a period that included the ESV's first edition in 2001 ^[7][15]. The data do not prove a causal link, but they show the phrase becoming far more common in print.

Which Bibles still say fornication?

Fornication survives mainly in the King James Version and in older or more traditional translations. The KJV keeps it in all 26 places ^[1], and the ASV and the Douay-Rheims keep it in 1 Corinthians 6:18 ^[3]. The New King James Version is mixed: it says "Flee sexual immorality" in 1 Corinthians 6:18 but keeps "committed fornication" in Revelation 17:2 ^[3][11].

The New American Standard Bible shows the shift within a single translation. Its 1977 and 1995 editions read "Flee immorality" in 1 Corinthians 6:18, while the 2020 edition adds the adjective: "Flee sexual immorality" ^[3]. Even a version that once preferred plain "immorality" in this verse has moved toward the same phrase.

The New Revised Standard Version of 1989 kept the word in several key verses, from "Shun fornication!" in 1 Corinthians 6:18 to "abstain from fornication" in 1 Thessalonians 4:3 ^[3][10]. Its 2021 revision dropped it in the first of these verses, where the NRSV Updated Edition reads "Shun sexual immorality!" ^[8], part of the roughly 25 changes that Liu describes ^[9].

The trend is not uniform toward "sexual immorality." The NRSV preferred "unchastity" in Matthew 5:32, the New American Bible chose "immorality" in 1 Corinthians 6:18, and the NIV used "adultery" in Revelation 17:2 ^[3][11][12]. Readers comparing versions are thus comparing interpretations of one Greek word, not simply old and new vocabulary.

Frequently asked questions

Is fornication in the NIV at all?

No. A BibleGateway keyword search for "fornication" returns no verse in the NIV, and the same is true of the ESV ^[4][5]. The NIV usually says "sexual immorality" and, in Revelation 17:2, "adultery" ^[3][11].

What is the difference between porneia and moicheia?

Moicheia means adultery and is narrow: it occurs four times in the Textus Receptus, always rendered adultery in the KJV ^[13]. Porneia is broader, covering illicit sexual intercourse in general and sometimes adultery itself ^[1]. The two appear side by side in lists such as Matthew 15:19 and Galatians 5:19 ^[13].

Which translation is most literal?

There is no single agreed answer, because "literal" can mean following words or following structure. The ESV calls itself "essentially literal" ^[7], while the NIV describes a balance between transparency to the original and clarity ^[6]. Young's Literal Translation goes furthest in 1 Thessalonians 4:3 with "abstain from the whoredom" ^[10].

Does sexual immorality include sex before marriage?

In the usual reading, yes: the lexicon definition of porneia lists fornication among the forms of illicit intercourse ^[1], and "sexual immorality" is meant to be at least as broad. Some scholars, such as Gerald C. Liu, argue that porneia did not simply mean sex before marriage ^[9].

Why does the NIV say adultery in Revelation 17:2?

Because the verse is figurative. Porneia and its verb there describe idolatry through a sexual image, a sense Strong's lists as figurative ^[11]. The NIV renders that image as "committed adultery" and "the wine of her adulteries," while the ESV keeps "sexual immorality" ^[11].

What does "flee fornication" mean?

It is the KJV rendering of 1 Corinthians 6:18, where Paul uses the Greek verb for flee or shun with porneia as its object ^[3]. Modern versions say "Flee from sexual immorality" (NIV, ESV) or "Run from sexual sin!" (NLT), while the 1989 NRSV said "Shun fornication!" ^[3]. The verse is read in context in our dedicated study of 1 Corinthians 6:18.