Th vs radiothorium

Th and radiothorium both are nouns.

Word	Noun	Adjective	Verb	Adverb
Th	Yes	No	No	No
radiothorium	Yes	No	No	No

As nouns, radiothorium is a hyponym of Th; that is, radiothorium is a word with a more specific, narrower meaning than Th:

Th: a soft silvery-white tetravalent radioactive metallic element; isotope 232 is used as a power source in nuclear reactors; occurs in thorite and in monazite sands
radiothorium: radioactive isotope of thorium with mass number 228

Other hyponyms of Th include thorium-228.

Th (noun)	radiothorium (noun)
a soft silvery-white tetravalent radioactive metallic element; isotope 232 is used as a power source in nuclear reactors; occurs in thorite and in monazite sands	radioactive isotope of thorium with mass number 228
the fifth day of the week; the fourth working day