WordNet sense 1 (a nonmetallic element belonging to the halogens; used especially in medicine and photography and in dyes; occurs naturally only in combination in small quantities (as in sea water or rocks)):

iodine, iodin

WordNet sense 2 (the smallest whole number or a numeral representing this number):

ace, one, single, unity

WordNet sense 3 (the 9th letter of the Roman alphabet):

letter i

WordNet sense 4 (used of a single unit or thing; not two or more):

ane

WordNet sense 5 (being or denoting a numerical quantity but not order):

cardinal