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

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

These liaisons are consensual but fraught by infidelity, disparities in age and power, shifting norms. —Judy Berman, Time, 5 Mar. 2026

In all probability, Noem’s fatal error was not infidelity, incompetence, or self-enrichment. —Jonathan Chait, The Atlantic, 5 Mar. 2026

Conventional political wisdom has it that Talarico was the stronger Democratic candidate in November, especially if Republicans nominate Paxton, a conservative firebrand who has weathered allegations of corruption and infidelity over the years. —Bill Barrow, Los Angeles Times, 4 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