adultery

noun

adul·​tery ə-ˈdəl-t(ə-)rē 

plural adulteries

: voluntary sexual intercourse between a married person and someone other than that person's current spouse

also : an act of adultery

Did you know?

What’s the difference between adultery and fornication?

In case you were wondering, the words adultery and adult are not etymologically related (in other words, adultery didn’t grow out of adult in the way that punditry grew out of pundit). Although both words come from Latin and share the same first five letters, adultery is from adulterāre (“to pollute, defile, commit adultery”), a word formed ultimately from the Latin elements ad- “to, near” and alter “other.” English adult comes from adultus, which is the past participle of the Latin word adolescere (“to grow up”).

In legal use there is a difference between adultery and fornication. Adultery is only used when at least one of the parties involved (either male or female) is married, whereas fornication may be used to describe two people who are unmarried (to each other or anyone else) engaging in consensual sexual intercourse.

Synonyms

• cheating
• misconduct
• infidelity

Examples of adultery in a Sentence

He found out that his wife had committed adultery.

She accused her husband of adultery.

Recent Examples on the Web

As China’s economy has grown, so too has its incidence of adultery. —Sheri Linden, HollywoodReporter, 23 Oct. 2025

Thou shalt not commit adultery. —Lina Ruiz, Fort Worth Star-Telegram, 22 Sep. 2025

Unhappy unions loom large in the novel, which teems with adultery. —Katy Waldman, New Yorker, 22 Sep. 2025

Angela Paxton filed for divorce in July, accusing her husband of adultery. —Lauren McGaughy, ProPublica, 17 Sep. 2025

Word History

Etymology

Middle English adultrye, adultery, alteration (conformed to Latin adulterium) of avoutrie, advoutrie, alteration (with addition of suffix -ie -y entry 2) of avoutre, borrowed from Anglo-French avulteire, avouteire, going back to Latin adulterium, from adulterāre "to defile by adultery, commit adultery with, pollute" + -ium deverbal noun suffix — more at adulterate entry 1

First Known Use

15th century, in the meaning defined above

Kids Definition

adultery

noun

adul·​tery ə-ˈdəl-t(ə-)rē 

plural adulteries

: voluntary sexual intercourse between a married person and someone other than his or her spouse

adulterer

-tər-ər

noun

adulteress

-t(ə-)rəs

noun

adulterous

-t(ə-)rəs

adjective

Legal Definition

adultery

noun

adul·​tery

ə-ˈdəl-tə-rē

: voluntary sexual intercourse between a married person and someone other than that person's current spouse

also : the crime of adultery compare fornication

adulterer

ə-ˈdəl-tə-rər 

noun

adulteress

-tə-rəs 

noun