unfaithful

Etymology

It is formed from English un- + faithful,^[2][3][4][5] first as Middle English unfeithful, from feithful.^[6][7][5] Faithful itself is formed from faith and -ful.^[3]

Earliest recorded meaning

Inconstant, faithless, not to be trusted: 1370–72, in a lyric about a faithless woman in a Shropshire deed.^[7] The sense "lacking religious faith, unbelieving" follows in the Wycliffite Bible from about 1382.^[7][2] Etymonline dates the word to the late 14th century,^[3] Dictionary.com to 1350–1400,^[5] and Merriam-Webster gives the 15th century.^[6]

Semantic evolution

In Middle English the word meant both "without proper religious faith" (also "not Christian, pagan", and as a noun, infidels) and "inconstant, treacherous".^[7] The OED's quotations for acting falsely or treacherously begin in 1530, with Palsgrave,^[2] and the word was applied to conduct lacking good faith from 1565 and to things from 1586, in Sidney's Arcadia.^[2] From 1697 it described a copy or translation that does not follow its original.^[2] Johnson (1755) defined it as "perfidious; treacherous", quoting Shakespeare.^[8] The modern main sense, unfaithful in marriage, is first recorded in Noah Webster's dictionary of 1828.^[2][3] Collins now labels both "lacking religious faith" and "dishonest" as obsolete.^[9]

Timeline

• 1370–72 – inconstant, faithless, treacherous.^[7]
• c. 1382 – lacking religious faith, unbelieving.^[7][2]
• 1565 – of conduct, dishonest, lacking good faith.^[2]
• 1586 – of things, not to be relied on.^[2]
• 1697 – of a copy or translation, inexact.^[2]
• 1828 – unfaithful in marriage.^[2][3]

Meanings

Adjective

1. Having sex or a sexual relationship with someone other than one's spouse or partner: He had been unfaithful to his wife for years.^[9][6][2]
2. Not keeping a promise, vow or duty; disloyal: an unfaithful ally.^[9][6][2]
3. Not accurate or exact; not true to an original: an unfaithful translation of the poem.^[9][2]
4. (obsolete) Having no religious faith; infidel.^[9][6][2]
5. (obsolete) Not upright; dishonest.^[9][2]

Word family

• unfaithfully
• unfaithfulness

Related words

• faithful
• faith
• faithless

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m n o p Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
5. ^ a b c Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
6. ^ a b c d e Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ a b c d e f Kurath, Hans; Kuhn, Sherman M.; Lewis, Robert E., eds. (1952–2001), Middle English Dictionary, Ann Arbor: University of Michigan Press; online edition ed. Frances McSparran et al. (2000–2018)
8. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
9. ^ a b c d e f Collins English Dictionary (2023), Glasgow: HarperCollins