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 or partner

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

Every look with such an irregular desire is in our Savior’s opinion a virtual adultery. . . . —Merve Emre, New Yorker, 16 June 2025

The sixth commandment in Catholic teaching prohibits adultery. —Ruth Graham, New York Times, 22 May 2025

If signed into law, divorces would only be allowed in cases of abandonment, gross neglect, extreme cruelty, habitual drunkenness, insanity for a period of five years, adultery, unknown pregnancy and fraudulent contract. —Saleen Martin, USA TODAY, 27 Jan. 2025

Directed by Jonathan Li and Choy Man-yu, the film stars Louis Koo as a private detective investigating a complex case involving adultery and murder. —Naman Ramachandran, Variety, 2 June 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