Noun
Hopf algebra (plural Hopf algebras)
English Wikipedia has an article on:Hopf algebraWikipedia
(mathematics) A structure that is simultaneously a unital associative algebra and a counital coassociative coalgebra, equipped with an antiautomorphism satisfying a certain property.
Representation ring of a group ring To any group ring or Hopf algebra is associated its representation ring or "Green ring". Source: Internet