Hinge

In a V-shaped polycule, the hinge is the person who is partnered with both of the other two. The other two people are partnered with the hinge but not with each other; they are metamours via the hinge. The hinge name comes from the shape: the central person on whom the V hinges open.

Being a hinge has a particular set of demands. The hinge is the practical communications conduit between two relationships that may have very different needs, schedules, and emotional rhythms. The hinge is the one whose time is split, whose attention is most fractured, whose calendar has to coordinate two separate relationships' worth of plans. Many polyamorous communities have a particular sympathy for the hinge role precisely because hinges often shoulder more of the practical and emotional logistics than the term implies.

Good hinging is a skill. Standard moves include: not relaying messages between metamours when those metamours could just talk to each other; not over-promising in either direction in a way that creates conflicts when the calendar reality intrudes; checking in proactively with both metamours about how the structure is feeling rather than waiting for either to raise it as a problem.

Pivot is a less-common synonym, used in some communities. The shape is the same; the role is the same.