Pt vs noble metal

Pt and noble metal both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pt	Yes	No	No	No
noble metal	Yes	No	No	No

As nouns, noble metal is a hypernym of Pt; that is, noble metal is a word with a broader meaning than Pt:

Pt: a heavy precious metallic element; grey-white and resistant to corroding; occurs in some nickel and copper ores and is also found native in some deposits
noble metal: any metal that is resistant to corrosion or oxidation

Pt (noun)	noble metal (noun)
a heavy precious metallic element; grey-white and resistant to corroding; occurs in some nickel and copper ores and is also found native in some deposits	any metal that is resistant to corrosion or oxidation