Section Functor_Assoc.
Context {C1 C2 C3 C4 : Category}
(F : (C1 –≻ C2)%functor)
(G : (C2 –≻ C3)%functor)
(H : (C3 –≻ C4)%functor).
Local Open Scope functor_scope.

Theorem Functor_assoc : (H ∘ G) ∘ F = H ∘ (G ∘ F).