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

These liaisons are consensual but fraught by infidelity, disparities in age and power, shifting norms. —Judy Berman, Time, 5 Mar. 2026

In all probability, Noem’s fatal error was not infidelity, incompetence, or self-enrichment. —Jonathan Chait, The Atlantic, 5 Mar. 2026

Conventional political wisdom has it that Talarico was the stronger Democratic candidate in November, especially if Republicans nominate Paxton, a conservative firebrand who has weathered allegations of corruption and infidelity over the years. —Bill Barrow, Los Angeles Times, 4 Mar. 2026

Conventional political wisdom has Talarico as the stronger Democratic candidate for November, especially if Republicans nominate Paxton, a conservative firebrand who has weathered allegations of corruption and infidelity over the years. —Bill Barrow, Twin Cities, 4 Mar. 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