Universal property of localization
= Universal property of localization
{wiki=Localization_(commutative_algebra)}
The localization map $\iota:R\to S^{-1}R$ sends every element of $S$ to a unit. If a ring homomorphism $f:R\to T$ also sends every element of $S$ to a unit, there is a unique homomorphism $\widetilde f:S^{-1}R\to T$ with $\widetilde f(r/s)=f(r)f(s)^{-1}$ and $\widetilde f\iota=f$.