A ring homomorphism is a map f:S→R between rings S and R such that
- f:(S,+)→(R,+) is a group homomorphism;
- f(s1s2)=f(s1)f(s2) for all s1,s2∈S;
- f(1)=1.
A ring isomorphism is a homomorphism that happens to also be a bijection.
Wikidata ID: Q1194212