Non-monogamy in the context of "Extramarital sex"

Infidelity (synonyms include cheating, having an affair, adultery, being unfaithful, non-consensual non-monogamy, straying or two-timing) is a violation of a couple's emotional or sexual exclusivity that commonly results in feelings of anger, sexual jealousy, and rivalry.

What constitutes infidelity depends on expectations within the relationship. In marital relationships, exclusivity is commonly assumed. Infidelity can cause psychological damage, including feelings of rage and betrayal, depression, low sexual and personal confidence, and even post-traumatic stress disorder. People of both sexes can experience social consequences if their act of infidelity becomes public, but the form and extent of these consequences can depend on the gender of the unfaithful person.

Monogamy (/məˈnɒɡəmi/ mə-NOG-ə-mee) is a relationship of two individuals in which they form a mutual and exclusive intimate partnership. Having only one partner at any one time, whether for life or serial monogamy, contrasts with various forms of non-monogamy (e.g., polygamy or polyamory).

The term monogamy, derived from Greek for "one marriage," has multiple context-dependent meanings—genetic, sexual, social, and marital—each varying in interpretation across cultures and disciplines, making its definition complex and often debated. The term is typically used to describe the behavioral ecology and sexual selection of animal mating systems, referring to the state of having only one mate at any one given time. In a human cultural context, monogamy typically refers to the custom of two individuals, regardless of orientation, committing to a sexually exclusive relationship.