Not polyamorous (at least to my knowledge,) but there are multiple times of polyamorous relationships
Two examples where there's 3 people involved:
-One can be compared to a triangle, where everyone is dating each other.
-Another is like a V, where one person is dating 2 people, but those two aren't dating each other, but are still consenting to the scenario.
So, if in this scenario it was with 3 people, it could go from a triangle to a V.
But there still can be more than 3 people in a polyamorous relationship. Really the most important thing is that everyone has to be consenting.