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

Tensions notably come to a head between Bennie and his sister-in-law, Lucretia (a game Wanda Sykes), because of his past infidelity, which provides some of the sitcom's funniest moments via razor-sharp one-liner wars. —Andrew Walsh, Entertainment Weekly, 5 Apr. 2026

Burden’s family legacy was fractured by infidelity and a laissez faire attitude, at least in the public sphere, toward men behaving badly. —Marc Weingarten, Los Angeles Times, 31 Mar. 2026

During the documentary, the former couple also discussed Odom's infidelity. —Ariana Quihuiz, PEOPLE, 31 Mar. 2026

Woods later admitted to infidelity and took a break from golf. —Megan Armstrong, MSNBC Newsweek, 31 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