To a large degree, open relationships are a generalization of the concept of a relationship beyond monogamous relationships. There are several different styles of open relationships. Some examples include:
Multi-partner relationships, between three or more partners where a sexual relationship does not occur between all of the parties involved.[3]
Hybrid relationships, when one partner is nonmonogamous and the other is monogamous.[3]
Swinging, in which singles or partners in a committed relationship engage in sexual activities with others as a recreational or social activity.
The term open relationship is sometimes used interchangeably with the closely related term polyamory, but the two concepts are not identical. The main unifying element to open relationship styles is non-exclusivity of romantic or sexual relationships.