iodine-131 iodine-125 • iodine absorption · · · Info · Definitions · Characters · · iodine-131 · · Text Common · · Latin · · Scripts 10 · · Length 3 · · Syllables Definitions · · · (noun) heavy radioactive isotope of iodine with a half-life of 8 days; used in a sodium salt to diagnose thyroid disease and to treat goiter. · · Noun Definition 1 Characters · · - hyphen-minus U+002D 1 digit one U+0031 3 digit three U+0033 d latin small letter d U+0064 e latin small letter e U+0065 i latin small letter i U+0069 n latin small letter n U+006E o latin small letter o U+006F