noun, plural ef·fi·cac·i·ties.
Examples from the Web for efficacity
"Confess the efficacity of the mass," cried the two bishops to poor Brown.History of the Reformation in the Sixteenth Century, Volume V|J. H. Merle d'Aubigné
The second question is that of knowing what is the rôle, the utility, and the efficacity of the psychical phenomenon.
If it is not the thing that creates the relation, it will be said, at least it is that which creates its efficacity of suggestion.