Adultery

thumb|Illustration depicting an adulterous wife, circa 1800

relationship between U.S. president Bill Clinton and Monica Lewinsky

thumb|The Jealous Husband (1847), a genre painting by [[Cornelius Krieghoff depicting a cuckolded husband]]

sexual intercourse outside a marriage

An affair is a relationship typically between two people, one or both of whom are either married or in a long-term monogamous or emotionally-exclusive relationship with another person. The affair can be solely sexual, solely physical, solely emotional, or a combination of these.

legal status of a child born to parents who are legally married (or later granted trought legitimization)

thumb|right|Blodeuwedd by Christopher Williams (Welsh artist)|Christopher Williams (1930) Blodeuwedd (; Welsh "Flower-Faced", a composite name from blodau "flowers" + gwedd "face"), is married to Lleu Llaw Gyffes in Welsh mythology. She was made from the flowers of broom, meadowsweet and oak by the magicians Math and Gwydion, and is a central figure in Math fab Mathonwy, the last of the Four Branches of the Mabinogi.

scandal involving Donald Trump and pornographic actress Stormy Daniels around sexual relations and an alleged hush payment by lawyer Michael D. Cohen in 2016

19th-century U.S. presidential scandal

A homewrecker (sometimes styled as home wrecker or home-wrecker) is a person, object or activity that causes or comes close to causing the breakup of a marriage (or similar partnership). The homewrecker is said to have taken one of the spouses away from the marriage, thus "wrecking" the marital home.

A cuckquean is the wife of an adulterous husband (or partner for unmarried companions), and the gender-opposite of a cuckold. In evolutionary biology, the term is also applied to females who are investing parental effort in offspring that are not genetically their own. Similar prying within a family is called wittoldry. The term is derived from Early Modern English dating back to 1562 and is composed of the terms cuck "someone whose partner is unfaithful" and quean ().