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

• disloyalty
• faithlessness
• falseness
• falsity
• inconstancy
• perfidiousness
• perfidy
• unfaithfulness

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

Research from the Journal of Family Psychology reveals that our attachment styles may also have a role to play in our likelihood of infidelity. —Mark Travers, Forbes.com, 1 May 2025

In August 2024, the Bronx rapper filed for divorce amid recurring rumors of infidelity. —Demicia Inman, VIBE.com, 16 Apr. 2025

Within the compulsively readable and entertaining pages of all her stories, Weiner loads complex issues that resonate in women’s lives – body image and weight shaming; motherhood and infertility; infidelity; addiction and substance abuse, just to name a few. —Samantha Dunn, Oc Register, 11 Apr. 2025

Is the fear of infidelity present in your relationship? —Mark Travers, Forbes, 16 Mar. 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