Quad

A quad is a four-person relationship structure in which all or some of the members are romantically or sexually involved.

Instead of monogamy, members of quads believe in polyamory or loving multiple people at once. Any gender and sexual orientation can be represented in a quad. For instance, a quad could consist of three women and one man or two heterosexual couples.

There are quads where members are free to date persons outside of the group relationship and quads that are closed or fidelitous. A quad is a three-person group that is the four-person counterpart of a triad.