Non-monogamy is a blanket term which covers several types of interpersonal relationships in which an individual forms multiple and simultaneous sexual and/or romantic bonds. This can be contrasted with its opposite, monogamy, and yet may arise from the same psychology. The term has been criticized as it may evoke to imply that monogamy is the norm and that any other way of relating is somehow a deviation of that norm.
Many non-monogamous terms are flexible in definition, because they are based on criteria such as 'relationship' or 'love' that are themselves variably defined. In addition, usage creates distinctions beyond the raw definitions of the words. Thus, even though some relationships might technically be considered both polygamous and polyamorous, 'polygamy' usually signifies a codified form of multiple marriage, based on established religious teachings, while 'polyamory' is based on the preferences of the participants rather than social custom or established precedent.
Forms of non-monogamy include:
casual relationship a physical and emotional relationship between two unmarried people who may have a sexual relationship
group marriage (also termed polygynandry), in which several people form a single family unit, with all considered to be married to one another
relationship anarchy, which do not divide relationships of partners and non-partners, but have a more flexible approach to relationships where everything is allowed so long as everyone can accept the agreement.
swinging, similar to open relationships, but commonly conducted as an organised social activity