Polyfidelity

Polyfidelity describes a closed romantic-and-sexual unit of three or more people, all of whom are partnered with each other or with members of the group, and none of whom are partnered or sexually active with anyone outside it. It is sometimes called closed polyamory. The unit functions like a group commitment: the boundary is around the polycule itself, not around any one pairing within it.

Polyfidelity is uncommon as an explicit organising principle. Many people enter a triad, quad, or larger formation with the assumption it will remain closed; a smaller subset name and commit to that closure as polyfidelity. The label tends to mean 'we are closed in the same way a monogamous couple is closed, but our number is larger than two.'

Polyfidelity has practical implications similar to monogamy at group scale: fluid bonding is feasible across the whole group; STI risk management is bounded; and decisions about new partners require group consent rather than individual choice. It also means the existing group structure has to absorb each member's full need for romantic-sexual connection, which can be sustaining when it works and crushing when one member's needs shift.

Risks: when one member of a polyfidelitous group develops feelings outside it, the structure has no built-in capacity for that — it must either re-negotiate openness, accept the new connection's exclusion (which can become resented), or break. Polyfidelity is not a magic stability solution; it is a different shape, with its own particular failure modes.