Let $(R, + ,\cdot)$ and $(S,\ast,\circ)$ be two rings and $f:R\to S$ a ring homomorphism. Then the function $$g:R/\ker{(f)}\to\operatorname{im}(f),\quad $g([x])=f(x)$$ a an isomorphism, called a ring isomorphism.
Thank you to the contributors under CC BY-SA 4.0!
