Wiktionary
linear operator
n. (context mathematics functional analysis English) An operator L such that for functions ''f'' and ''g'' and scalar λ, L (''f'' + ''g'') = L ''f'' + L ''g'' and L λ''f'' = λ L ''f''.
WordNet
linear operator
n. an operator that obeys the distributive law: A(f+g) = Af + Ag (where f and g are function)