They also have implicational and non-implicational forms. Universals have also been connected to implicational laws. Number marking provides an example of implicational hierarchies in morphology. Implicational hierarchies also play a role in syntactic phenomena. The implicational calculi below use modus ponens as an inference rule. Additionally, implicational fragment of bunched logic has been given a games semantics. These axioms describe classical propositional logic; without axiom P4 we get positive implicational logic. However, most tendencies, like their universal counterparts, are implicational.