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

The post was accompanied by a series of hashtags that included #divorce, #cheating and #infidelity. —The Athletic Mlb Staff, New York Times, 21 June 2025

The series boasts all the good bone structure of a traditional family drama, with threads of criminality, infidelity, lies, drugs and everything in between woven throughout each episode. —Aramide Tinubu, Variety, 19 June 2025

Driven by a dramatic arrangement and Christie's operatic falsetto, the single told the story of a young man torn between love and infidelity — and captured a uniquely teenage mix of angst and bravado. —Dave Quinn, People.com, 19 June 2025

Creators shared videos about pregnancy horror stories, infidelity and threats of domestic violence, opening up a conversation about how young people use humor as a coping mechanism to talk about traumatic events. —Rachel Hale, USA Today, 19 June 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