infidelity

noun

in·​fi·​del·​i·​ty ˌin-fə-ˈde-lə-tē 

-(ˌ)fī-

plural infidelities

1

a

: the act or fact of having a romantic or sexual relationship with someone other than one's spouse or partner

b

: unfaithfulness to a moral obligation : disloyalty

infidelity to the group's guiding principles

2

: lack of belief in a religion

Synonyms of infidelity

• adultery
• betrayal

Examples of infidelity in a Sentence

She was convinced that her husband was guilty of infidelity.

He has admitted to a number of marital infidelities.

Recent Examples on the Web

Sullivan also accused Morgan’s wife, the journalist and author Celia Walden, of pining for infidelity in her social media posts. —Jake Kanter, Deadline, 19 Mar. 2026

Josh apologized for marital infidelity and a pornography addiction at the time and sought treatment. —Brie Stimson, FOXNews.com, 19 Mar. 2026

While Huerta has never spoken before about Chavez’s attacks on her, his infidelities and autocratic leadership style — and rumors of misconduct — have been documented for years. —Los Angeles Times, 18 Mar. 2026

All the secrets pour out, the revelations of infidelity and addiction and so on, as the group gives vent to the stuff that’s previously been unsayable—not to fix anything, mind you, since some things can’t be fixed. —Emily Nussbaum, New Yorker, 12 Mar. 2026

Word History

Etymology

Middle English infidelite, borrowed from Middle French infidelité, borrowed from Latin infidēlitāt-, infidēlitās "faithlessness, inconstancy," from infidēlis "unfaithful, disloyal" + -itāt-, -itās -ity — more at infidel entry 2

First Known Use

15th century, in the meaning defined at sense 2

Rhymes for infidelity

• fidelity

Kids Definition

infidelity

noun

in·​fi·​del·​i·​ty ˌin-fə-ˈdel-ət-ē 

-(ˌ)fī-

plural infidelities

1

: lack of faith in a religion

2

: unfaithfulness especially to one's husband or wife