A quad is a type of relationship structure involving four people. Only some or all of the members of a quad may be romantically or sexually involved with one another.
People involved in quads believe in polyamory, or loving more than one person at the same time, rather than monogamy. The people in a quad may be of any gender and sexuality. For example, a quad may be made up of two straight couples or three females and one male.
There are closed or fidelitous quads and quads where the members are free to date other people outside the group relationship. A quad is the four-person equivalent of a triad, which contains three people.
