In group theory, a subgroup of a group is termed malnormal intersect only in the identity element.

Some facts about malnormality:

• The intersection of malnormal subgroups is malnormal.

  Malnormality is transitive; that is, a malnormal subgroup of a malnormal subgroup is malnormal.

  The trivial subgroup and the whole group are malnormal subgroups. A normal subgroup that is also malnormal must be one of these.

  Every malnormal subgroup is a special type of C-group called a trivial intersection subgroup, or TI subgroup.

is finite is called a "Frobenius complement". is the semidirect product.

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