A canonical derivation in logic is one satisfying some set of conditions that are laid down: thus it may be important to show that if there is a derivation of B from A, there is a particular kind of derivation, en route to showing some result of proof theory. More widely the term may refer to a derivation which mirrors the structure of what is proved, as opposed to an indirect derivation that does not. A canonical description of a sentence would be one that revealed its basic structure or showed how the sentence is built by transformations from a basic structure.