Formal group law
= Formal group law
{wiki}
A one-dimensional commutative formal group law over a ring $R$ is a series $F(X,Y)\in R[[X,Y]]$ satisfying the identity, commutativity, and associativity axioms. A homomorphism from $F$ to $G$ is a series $\theta(T)\in TR[[T]]$ satisfying $\theta(F(X,Y))=G(\theta(X),\theta(Y))$.