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 husband, wife, or partner

b

: unfaithfulness to a moral obligation : disloyalty

2

: lack of belief in a religion

Synonyms

• 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

Researchers set out to explore why public reactions to celebrity infidelity vary so widely. —Mark Travers, Forbes.com, 8 July 2025

The source also claimed that there were multiple instances of infidelity. —Jason Pham, StyleCaster, 8 July 2025

In Just Keke, Palmer explores the not-so-pretty side of love, and many will be able to relate to the uncomfortable truths that come along with infidelity and broken bonds. —Lynnette Nicholas, Essence, 7 July 2025

The Secret Lives of Mormon Wives is gearing up for a wild season 3 after last season ended with a shocking allegation of infidelity. —EW.com, 3 July 2025

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