In mathematics, in the field of group theory, a subgroup H of a given group G is a subnormal subgroup of G if there is a finite chain of subgroups of the group, each one normal in the next, beginning at H and ending at G. In notation,
-subnormal for some positive integer
Some facts about subnormal subgroups: The property of subnormality is transitive, that is, a subnormal subgroup of a subnormal subgroup is subnormal.
The relation of subnormality can be defined as the transitive closure of the relation of normality.
If every subnormal subgroup of G is normal in G, then G is called a T-group.