and sometimes interchangeable. but there are some distinctions that are worth defining. For example, swingers may intentionally avoid emotional and social connection to those—other than their primary partner—with whom they have sex, so may or may not be polyamorous but are non-monogamous. Some useful terms are Metamour or Meta, the common term for a person with whom a partner is shared, V-Structure, one person is equally involved with two partners, and Triads / Quads. The latter is when three or four participants make up the primary partnership. Forms of non-monogamy are varied. They include a casual relationship, sometimes called friends with benefits, which is a primarily physical relationship between two people with low expectations of commitment or emotional labor, and an open relationship (incl. open marriage), referring to one or both members of a committed (or married) couple have the express freedom to become sexually active with others, Other forms include sexual activities involving more than two participants at the same time, referring to group sex orgies, and threesomes, a primarily sexual arrangement involving three people. There's also relationship anarchy where participants are not bound by set rules in relationships other than whatever is explicitly agreed upon by the people involved, and swinging, which refers to similar to an organized social activity, often involving some form of group sex and sometimes simply trading partners with other swingers. There's also concepts such as Polyfidelity, where participants have multiple partners but restrict sexual activity to within a certain group, and a situation where there is a main romantic relationship with all other relationships being second to it, known as primary/secondary. One of the most well-known forms is polygamy, where one person is married to multiple partners. This has two primary sub-forms: polyandry where a woman has multiple husbands, group or conjoint marriage, and polygyny, referring to a man has multiple wives. The latter is more widespread in Africa than in any other continent, especially in West Africa and in North America, it is practiced by some Mormon sects, such as the Fundamentalist Church of Jesus Christ of Latter-Day Saints (FLDS Church). Although its sometimes confused with it, there is polyamory, referring to when participants have multiple romantic partners It comes in various forms, such as hierarchical polyamory, where there is a primary romantic relationship with all other relationships being secondary to it, kitchen table polyamory which refers to people are expected to