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

Huston could recognize the ways of that brood: her own renowned and eccentric family inhabited that domestic world of privilege, power, infidelity, and intrigue that became Christie’s writerly milieu. —Erik Morse, Vogue, 15 Apr. 2025

The exciting news comes after a tumultuous few months for Coi, who kicked off 2025 by announcing a child with Trippie before accusing him of infidelity. —Mackenzie Cummings-Grady, Billboard, 15 Apr. 2025

Harper’s husband, Ethan Spiller (played by Will Sharpe), then confronted Daphne about the infidelity. —Brian Anthony Hernandez, People.com, 14 Apr. 2025

Was there pushback against your using gospel to talk about infidelity? —Marcus J. Moore, Time, 9 Apr. 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