basic subgroup

《Lecture Notes on Bayesian Estimation and Classification》 · 第 107 页 · Section 4.3「Pure Subgroups and p-Groups」，小节「Basic Subgroups」

Let $G$ be an abelian torsion group. A subgroup $B$ is called a basic subgroup if it is pure in $G$, it is a direct sum of cyclic groups, and $G/B$ is divisible.