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

Nader reportedly ended things due to suspecting Savchenko of infidelity. —Maureen Lee Lenker, EW.com, 8 Apr. 2025

Not this evil man blaming Tracy for his infidelity! —Emma Specter, Vogue, 28 Mar. 2025

Clay, still reeling from Kaya’s infidelity, recoils at this request. —Lovia Gyarkye, The Hollywood Reporter, 8 Mar. 2025

Even arguments, negative talk about the other parent or exposure to adult problems like finances or infidelity can create lasting emotional wounds. —Ascend Agency, New York Daily News, 7 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