Change of rings
In algebra, a change of rings is an operation of changing a coefficient ring to another. == Constructions == Given a ring homomorphism f : R → S {\displaystyle f:R\to S} , there are three ways to change the coefficient ring of a module; namely, for a right R-module M and a right S-module N, one can form f ∗ M = M ⊗ R S {\displaystyle f^{*}M=M\otimes _{R}S} , the induced module, formed by extension of scalars, f !