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

Sturla Holm Lægreid’s spectacular on-air confession of infidelity didn’t win him any points with his ex-girlfriend. —James Hibberd, HollywoodReporter, 11 Feb. 2026

Lægreid, who previously won gold in the relay at the Beijing Olympics in 2022 and has 14 world championship medals to his name, explained on Tuesday that he was prompted to address the breakup and infidelity publicly in the hopes of reconciliation. —Shania Russell, Entertainment Weekly, 11 Feb. 2026

Moments after claiming bronze in Tuesday’s 20-kilometer men’s biathlon, Norway’s Sturla Holm Laegreid used the spotlight to make an emotional confession about infidelity and lingering feelings for his former partner. —Denny Alfonso, New York Times, 11 Feb. 2026

When asked about his infidelity, Lægreid’s teammate Johannes Dale-Skjevdal said some fellow athletes were aware of the incident. —Angela Yang, NBC news, 10 Feb. 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