A modified symmetric group is any member of a certain sequence of classical orthogonal matrix groups.
For every the modified symmetric group for dimension is the subgroup of the general linear group given by all permutation -matrices multiplied by a factor of or , i.e., the set
where .
The modified symmetric group for dimension , where , can also be defined as the direct product of groups of the cyclic group of order and the symmetric group for dimension .
The modified symmetric groups are an easy family of compact matrix quantum groups, i.e., the intertwiner spaces of their corepresentation categories are induced by a category of partitions. More precisely, it is the category of partitions of even size that induces the corepresentation categories of . Its canonical generating set of partitions is .