Plethysm

In algebra, plethysm is an operation on symmetric functions introduced by Littlewood (1936, p. 52, 1944, p.329), who denoted it by {λ}⊗{μ}. The word "plethysm" for this operation (after the Greek word πληθυσμός meaning "multiplication") was introduced later by Littlewood (1950, p.289, 1950b, p.274), who said that the name was suggested by M. L. Clark.

If symmetric functions are identified with operations in lambda rings, then plethysm corresponds to composition of operations.