(sports, jargon) A group in a multi-stage tournament which is unusually competitive, because the number of strong competitors in the group is greater than the number of qualifying places available for the next phase of the tournament.

(medicine) The basic system of categorizing blood by antigen type.

A group of musicians who regularly perform together.

plural of music group

Alternative form of abelian group

plural of Abelian group

plural of galaxy group

(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).