A partnership is a simultaneous sexual and social community between two people. It is a commonly studied twosome relationship. As a modern generic term, the term since the 1970s refers to all permanent sexual relations, regardless of the legal form of the relationship and regardless of the sexual orientation and the household and living conditions of those involved. The term partnership may thus include:

Marriages, registered partnerships, marriage-like communities (wild marriages) and firm love relationshipssame-sex and mixed-gender communitiesCohabitation, relationships of couples without a common household, and long-distance relationshipsA partnership is sexually motivated, at least in its origin, whereby the long-term development of the sexuality of the couple as a criterion of definition is irrelevant; The term may include sexually active couples as well as sexually inactive couples or couples living in an open relationship. Communities and life partnerships of friends, siblings u. a., between which there are no sexual relations, but are not referred to as a partnership. Pure sex relationships, on the other hand, do not meet the definition criteria for a partnership because they lack social cohesion.

In a narrower sense, partnership also refers to the self-commitment that two people who meet on an equal footing enter into a lasting sexual relationship.