The word canonical is used to indicate a particular choice from of a number of possible conventions. This convention allows a mathematical object or class of objects to be uniquely identified or standardized.
For example, the right-hand rule for the cross product is a convention, which corresponds to the canonical vector
space orientation in .
Similarly, canonical labeling provides a way
to uniquely label a graph so that isomorphism checking is reduced to comparing canonical
labelings of two graphs.