A plethory is a monoid object in the monoidal category of birings. The most famous example of such a creature is Λ\Lambda, the ring of symmetric polynomials. See:

  • J. Borger, B. Wieland, Plethystic algebra, Advances in Mathematics 194 (2005), 246–283. (web)
Created on June 29, 2010 00:31:03 by John Baez (