I don’t remember epistasis but polygenic inheritance is when a single trait is determined by more than one gene.

I think epistasis is when you have a pair of genes that control the same trait where one set is dominant masks whatever the other set is.

Epistatis is a form of gene interaction in which one gene masks the phenotypic expression of another. Polygeneic inheritance is when multiple genes are involved in the phenotypic expression of a single trait. Its not really an either or thing, I’m sure (though I can’t think of one off the top of my head) that there are epistatic elements to some polygenic traits.

-Jelanen