Every finite abelian extension of $\QQ$ lies inside a cyclotomic field.Suggest a slogan
Let \(K\subseteq\CC\) be a finite Galois extension of \(\QQ\) with \(\Gal(K/\QQ)\) abelian. Then there is an integer \(m\geq 1\) such that \(K \subseteq \QQ(\zeta_m)\), where \(\zeta_m\coloneqq e^{2\pi i/m}\).