# Ring homomorphism from field

If we have homomorphism from field K to ring R, does that mean that we have ring homomorphism but K is a field?

I have trouble understanding this. Thank You very much for your help.

Think about what it means for $K$ to be a field: it means that $K$ is a commutative, unital ring with inverses. So, we can also think of $K$ as being a ring, so a homomorphism from $K$ to $R$ likely refers to a ring homomorphism.
The only ideals in a field $K$ are $0$ and $K$, so since the kernel is an ideal, every homomorphism out of a field is either bijective and hence an isomorphism, or the zero map.