for subgroups
The condition on a group that every proper subgroup is strictly contained in its normalizer (cf. Normalizer of a subset). Every group satisfying the normalizer condition is a locally nilpotent group. On the other hand, all nilpotent groups, and even groups having an ascending central series ($ZA$-groups), satisfy the normalizer condition. However, there are groups with the normalizer condition and with a trivial centre. Thus, the class of groups with the normalizer condition strictly lies in between the classes of $ZA$-groups and locally nilpotent groups.
| [1] | A.G. Kurosh, "The theory of groups" , 1–2 , Chelsea (1955–1956) (Translated from Russian) |
| [a1] | D.J.S. Robinson, "A course in the theory of groups" , Springer (1980) |