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 research points to a common issue in monogamous couples: infidelity. —Paul Du Quenoy, MSNBC Newsweek, 26 Mar. 2025

In various texts, including Apocryphal works that date to around the same time as the Gospels proper, Joseph appears to suspect Mary of infidelity. —Adam Gopnik, The New Yorker, 24 Mar. 2025

Additionally, many individuals also hesitate to date bisexual people due to unfounded fears of infidelity, forcing bisexual individuals to constantly justify their identity based on their current or past partners. —Mark Travers, Forbes, 24 Mar. 2025

Shakespeare’s tragedy — penned around 1603, under its full name: The Tragedy of Othello, the Moor of Venice — follows Othello as Iago manipulates him into suspecting Desdemona of infidelity. —Dave Quinn, People.com, 21 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