Polyfidelity

Polyfidelity is a polyamorous structure with a hard boundary around it: three or more people who are partnered with each other (or with members of the group), with no openness to additional partners outside that group. The internal shape is polyamorous; the external boundary functions like monogamy at group scale.

Common shapes are triads (three people each partnered with the other two), quads (four people in various internal pairings), and occasionally larger group families. The label polyfidelity is most useful when applied deliberately — the group has named its closed boundary, agreed to it, and structured its life around it.

Polyfidelitous arrangements have advantages: fluid bonding becomes feasible across the whole group; STI risk management is bounded; decisions about new partners are unnecessary because new partners aren't sought; the group becomes its own complete social unit in a way larger, open polycules typically are not. For some people in some life stages, this combination is exactly right.

The risks are predictable. When one member develops feelings outside the closed group, the structure has no built-in flexibility to absorb that — the choice is either re-opening (which requires the whole group's consent), accepting the exclusion of the new connection (often resented), or breaking. Polyfidelity is sometimes assumed to be more stable than open polyamory; in practice the rigidity that makes it appealing in one period is what causes it to break in another.

Polyfidelity is sometimes a stage rather than a permanent structure. A triad or quad may go through a polyfidelitous period — focused on consolidating itself as a group — and later re-open as the group matures and individual members want flexibility again. Treating polyfidelity as the natural end-state for triads (or quads) is often an error.