A subgroup of S n that is generated by transpositions is called a Young subgroup. They are all of the form S a 1 × × ⋯ ⋯ × × S a ℓ ℓ where ( a 1 , … … , a ℓ ℓ ) is an integer partition of n. These groups may also be characterized as the parabolic subgroups of S n when it is viewed as a reflection group.