relatum. We say that a relation and its converse have opposite "senses"; thus the "sense" of a relation that goes from
to
is the opposite of that of the corresponding relation from
to
. The fact that a relation has a "sense" is fundamental, and is part of the reason why order can be generated by suitable relations. It will be observed that the class of all possible referents to a given relation is its domain, and the class of all possible relata is its converse domain.