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

When men publicly fail through addiction, infidelity, financial collapse or reckless behavior there can be room for complexity. —Maia Niguel Hoskin, Forbes.com, 22 May 2026

The last season of the beloved sitcom had thrown fans for a loop, from Dan Conner's infidelity to the family's post-lottery win lifestyle. —Angela Andaloro, PEOPLE, 21 May 2026

Paxton’s baggage Cornyn’s runoff strategy has leaned heavily on Paxton’s ethical and legal history — the 2023 House impeachment and ongoing scrutiny of his conduct as attorney general and allegations of infidelity in his personal life. —Fort Worth Star-Telegram, 19 May 2026

In 1672, Antonia Bembo – then living in the back part of a house known as Cà Bembo in the neighborhood of Santa Maria Nova – sued for divorce, citing Lorenzo’s infidelity along with mental and physical abuse. —Claire Fontijn, The Conversation, 18 May 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