A multigrade operator Ω is a parametric operator with parameter k in the set ℕ of non-negative
integers.
The application of a multigrade operator Ω to a finite sequence of operands (x1,…,xk) is typically
denoted with the parameter k left tacit, as the appropriate application is implicit in the number of
operands listed. Thus Ω(x1,…,xk) may be taken for Ωk(x1,…,xk).
