is a left-derivation but not a derivation on M2(S).
Analogously we can define a right derivation on S as follows.
Definition 3.3 Let S be a semiring and X be a right-Smodule. An additive
map dR : S → X is said to be a right-derivation if dR(xy) = dR(x)y +
dR(y)x ∀ x, y ∈ S.