infidelity

American  

[in-fi-del-i-tee] / ˌɪn fɪˈdɛl ɪ ti /

noun

• infidelities
  plural

1. marital disloyalty; adultery.

2. unfaithfulness; disloyalty.

3. lack of religious faith, especially Christian faith.

4. a breach of trust or a disloyal act; transgression.

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infidelity British  

/ ˌɪnfɪˈdɛlɪtɪ /

noun

1. lack of faith or constancy, esp sexual faithfulness

2. lack of religious faith; disbelief

3. an act or instance of disloyalty

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Other Word Forms

Noun Inflected Forms

• infidelities
  plural

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Etymology

Origin of infidelity

First recorded in 1375–1425; late Middle English, from Latin infidēlitās; equivalent to infidel + -ity

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Explanation

Someone guilty of infidelity is cheating on a spouse or romantic partner. A common cause of divorce and heartbreak is infidelity. Fidel means "faithful" or "loyal." Tack on the prefix in, which means "not," and you've got yourself infidelity — the act of being unfaithful. The word can also be used to refer to someone's religious beliefs. Run angrily through a church and claim that God doesn't exist, and your fellow churchgoers will think you lack faith, or that you are guilty of infidelity.

Example Sentences

See Examples For:

infidelity infidelities

Mulligan argued that evidence of infidelity was not evidence of murder and questioned why Flynn was being accused of tampering with evidence because his gun could not be found.

From BBC ● Oct. 5, 2026

It used to be said that infidelity and money woes were the main causes of broken marriages.

From Los Angeles Times ● Jul. 1, 2026

His wife, state Sen. Angela Paxton, is divorcing him on “biblical grounds,” accusing him of infidelity.

From Salon ● Jun. 17, 2026

In the album, Allen leveled several shocking accusations about Harbour’s alleged infidelity, with the townhouse playing a central role in the record’s title track.

From MarketWatch ● Apr. 22, 2026

Up until the time of Harriet’s discovery of John Tubman’s infidelity, she had been guiding escaping slaves to the North and freedom largely because she wanted to rescue members of her own family.

From "Harriet Tubman: Conductor on the Underground Railroad" by Ann Petry

Melania Trump has in the past been sensitive to discussions of Trump’s infidelities.

From Slate ● Aug. 21, 2026

In middle age, Delery Anhalt has moved back to her hometown of New Orleans from Washington, D.C., after learning about her husband’s infidelities.

From The Wall Street Journal ● Apr. 23, 2026

While hailing King as “one of America’s founding fathers,” Eig doesn’t stint on his personal struggles and flaws, including his marital infidelities and posthumous revelations of plagiarism in his doctoral dissertation.

From New York Times ● Mar. 19, 2024

As controversial as their infidelities were, Cruz believes Rivera’s final request to unite with Kahlo in death was a sign of redemption.

From Los Angeles Times ● Nov. 28, 2023

Of course, Tía Fidelina, our uncle's wife, who is sweet and dedicated to La Virgen, "knows nothing" about Tío Orlando's infidelities.

From "How the García Girls Lost Their Accents" by Julia Alvarez

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Related Words

• adultery
• affair
• betrayal
• duplicity
• treachery

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