infidelity

Etymology

It is inherited from Middle English infidelite,^[2] borrowed from Old French infidelité^[2][3][4][5] and directly borrowed from Latin infidēlitās (“unfaithfulness, faithlessness”),^[3][4][6][7] from infidēlis (“unfaithful, unbelieving”) and the suffix -tās.^[4][7] The Latin adjective, the source of infidel, is formed from in- (“not”) and fidēlis (“faithful”).^[3] In Old French the word is recorded about 1170, of the Christian faith,^[4] and in post-classical Latin it meant lack of religious faith from the 4th century and treachery from the 7th.^[4] The OED compares infedeltà and infidelidad.^[4] Merriam-Webster gives the source as Middle French infidelité.^[8]

Earliest recorded meaning

False belief, unbelief in the Christian faith, and disloyalty: all three senses are in the Middle English Dictionary's quotations from the first half of the 15th century, the earliest in a translation of Higden.^[2] Etymonline dates the word to about 1400,^[3] Dictionary.com to 1375–1425,^[7] and the OED, whose entry has not been fully revised, to 1509, in Barclay's Shyp of Folys.^[4]

Semantic evolution

In Middle English the word belonged mainly to religion, for paganism or lack of faith;^[2][3] from the late 16th century it was also used of the beliefs of other religions, especially Islam, a sense obsolete by about 1700.^[4] The sense of disloyalty to a person was first used of a sovereign, lord or master,^[3][4] and in the 16th century also of a lover or spouse,^[3] which is the main sense today.^[4][5] An infidelity, a single unfaithful act, is recorded from 1714, in the Spectator.^[4] Johnson (1755) defined it first as want of faith and then as disbelief of Christianity.^[9] The general sense of disbelief or incredulity, from 1578, is now archaic,^[4][8] and Merriam-Webster also records a failure to copy something exactly.^[8]

Timeline

• c. 1425 – false belief, lack of faith, and disloyalty.^[2]
• 1509 – unbelief in religious matters, especially in Christianity.^[4]
• 1529 – unfaithfulness or disloyalty to a person.^[4]
• 1578 – disbelief, incredulity in general.^[4]
• 1597 – the beliefs of a religion other than Christianity (obsolete by 1700).^[4]
• 1714 – an act of unfaithfulness.^[4]

Meanings

Noun

1. Romantic or sexual unfaithfulness to one's husband, wife or partner, or a single act of it: The marriage did not survive his infidelity.^[8][10][4]
2. Disloyalty; a breach of trust or of a duty.^[8][10][4]
3. Lack of religious faith, especially in Christianity.^{[8][10][4][5]}
4. A failure to reproduce something, such as a text, exactly.^[8]
5. (archaic) Disbelief or incredulity in general.^[8][4][5]

Related words

• infidel
• fidelity
• faith
• perfidy

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e 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)
3. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c d e f g h i j k l m n o p q r s t u Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
5. ^ a b c d Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
6. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
7. ^ a b c Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
8. ^ a b c d e f g h Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
9. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
10. ^ a b c Collins English Dictionary (2023), Glasgow: HarperCollins