- iodine, iodin, I, atomic number 53 - 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)
--1 is a kind of chemical element, element; halogen
--1 is a substance of seawater, saltwater, brine
--1 has particulars: iodine-131; iodine-125