Closed Triad
three people who all know each other isn't just a friend group - it's a trust machine you can't lie inside of
Grounded in the research on Wikipedia: Triadic closure; Georg Simmel on the triad (1908); James Coleman, 'Social Capital in the Creation of Human Capital' (1988)
so what even is this?
A closed triad is three people where all three know each other. Not A knows B, B knows C - everyone's tied to everyone. That little triangle is the smallest closed shape a network can make, and it behaves completely differently from an open chain. Once your two friends become friends, the gap closes, and suddenly there's no private side of the relationship anymore. The triangle sees everything.
where did it come from?
Georg Simmel, German sociologist, nailed it in 1908: going from two people to three isn't just +1, it changes the whole game. A pair can collapse if one leaves; a triad can outlive any single member and gang up two-against-one. James Coleman (1988) added the payoff - closed networks create 'closure,' which lets a group actually enforce trust. Real, foundational sociology, not a guru coinage.