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

Following the news breaking, rumors of infidelity on both sides began circulating on social media. —Lori A Bashian, FOXNews.com, 19 June 2026

The Apartment is a daring dissection of toxicity in the story of an insurance clerk (Jack Lemmon) who lets his co-workers use his apartment to support their infidelity. —Brian Tallerico, Vulture, 19 June 2026

Bunnie Xo would eventually forgive Jelly Roll for his infidelity. —Raechal Shewfelt, Entertainment Weekly, 19 June 2026

That factored into her willingness to give her husband a second chance after his infidelity. —Lisa Respers France, CNN Money, 16 June 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