 Krasner's lemma

Let $K$ be complete, let $\alpha$ be separable over $K$, and let $\beta$ be algebraic over $K$. If $\beta$ is closer to $\alpha$ than any other $K$-conjugate of $\alpha$, then

Krasner's lemma is a result in the field of number theory, specifically dealing with linear forms in logarithms of algebraic numbers. It provides conditions under which a certain linear combination of logarithms can lead to a rational approximation or a specific form of representation. The lemma is often used in Diophantine approximation and transcendency theory.