What is "plethysm"

In algebra, plethysm is an operation on symmetric functions introduced by , who denoted it by {λ}⊗{μ}. The word "plethysm" for this operation (after the Greek word πληθυσμός meaning "multiplication") was introduced later by , 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.