If you have a unary function F, you can compose it with function G, H = F ∘ G, which means H(x) = F(G(x)). Instead of running x through F directly, you run it through G first and then run the output of G through F.
If F is a binary function, then you either compose it with a unary function G on the left input: H = F ∘left G, which means H(x, y) = F(G(x), y) or yo...