St. Bonaventure on the making of books:

Sometimes a man writes others’ words, adding nothing and changing nothing; and he is simply called a scribe [scriptor]. Sometimes a man writes others’ words, putting together passages which are not his own; and he is called a compiler [compilator]. Sometimes a man writes both others’ words and his own, but with the others’ words in prime place and his own added only for purposes of clarification; and he is called not an author but a commentator [commentator]. Sometimes a man writes both his own words and others’, but with his own in prime place and others’ added only for purposes of confirmation; and he should be called an author [auctor].

Translation cited from J. A. Burrow, Medieval Writers and Their Work: Middle English Literature 1100-1500 (Oxford: Oxford University Press, 2nd ed. 2008), 31.