Algebraic Number Theory
《Algebraic Number Theory》 · 第 278 页 · Chapter V，Section 3「Kummer Extensions」
Assume that $K$ contains the group $\mu_n$ of $n$th roots of unity. Extensions of the form $L=K(\sqrt[n]{\Delta})$, obtained by adjoining $n$th roots of elements of a subgroup $\Delta\subset K^*$, are called Kummer extensions.