(astronomy) A group of galaxies that hold together gravitationally.

(group theory) A group obtained from a larger group by aggregating elements via an equivalence relation that preserves group structure.

(group theory) The unique group (up to isomorphism) consisting of a single element (which is the identity element).

(group theory) A group which has no normal subgroups apart from the trivial group and itself.

(group theory) a group of symmetries of a regular polygon

(group theory) a group of even permutations of a finite set

(algebra, group theory) A group whose elements are permutations (self-bijections) of a given set and whose group operation is function composition.

(group theory) A group whose elements represent ways to weave some number of strings into braids.

(group theory) Any one of the 26 exceptional finite simple groups, which do not belong to any of the general, infinite categories specified by the classification theorem for finite simple groups.

(group theory) A group generated by a single element.