axiom AA5 states:

p,q in P, h in H, and (h1,..,h(i-1),p,h(i+1),..,hn)>(h1,..,h(i-1),q,h(i+1),..,hn)

for some i => forall non-null j, (h1,..,h(j-1),p,h(j+1),..,hn)>(h1,..,h(j-1),q,h(j+1),..,hn)