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

Donald and Ivana split in 1990, following tabloid reports of infidelity and volatile fights. —Meredith Kile, PEOPLE, 1 May 2026

The Grammy winner, 31, who debuted late last month as Zidler in the Tony-winning adaptation of the 2001 musical film, will now be taking her final bow on Friday — less than a week after her post Saturday accusing 36-year-old Thompson of infidelity. —Jami Ganz, New York Daily News, 28 Apr. 2026

Authorities painted a picture of fights and arguments — including when Ashley accused him of infidelity — that ratcheted up to the killings. —Meredith Colias-Pete, Chicago Tribune, 28 Apr. 2026

Pugh had filed for a divorce for infidelity, said Troy Brown, the husband of one of the women who was shot and father to one of the deceased children. —Zoe Sottile, CNN Money, 20 Apr. 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