ix(n = noun.quantity) 9, ennead, nina from carolina, nine, niner - the cardinal number that is the sum of eight and one;
is a kind of digit, figure

   ix(s = adj.all) 9, nine - denoting a quantity consisting of one more than eight and one less than ten;

   The Roman numerals signifying nine; denoting a quantity consisting of one more than eight and one less than ten. [WordNet 1.5]

charles ix, factor ix, leo ix, louis ix, pius ix