Non-monogamy (or nonmonogamy) is an umbrella term that describes a relationship arrangement where one or more partners are not sexually and/or romantically exclusive to each other. Monogamy and non-monogamy are not strictly binary categories, but rather exist on a continuum encompassing various degrees of exclusivity and openness - at one end of this continuum lie strictly monogamous relationships, while at the other end are openly non-exclusive arrangements with numerous nuanced forms of varying degrees of openness in between. Non-monogamous relationships have been practiced across cultures and throughout history, reflecting diverse social norms, legal frameworks, and personal preferences.
In contemporary discourse, non-monogamy is understood to encompass a variety of practices, ranging from culturally institutionalised arrangements like polygamy to consensual agreements such as open relationships and polyamory, as well as non-consensual forms like infidelity.