thiamine vs B-complex vitamin

thiamine and B-complex vitamin both are nouns.

Word	Noun	Adjective	Verb	Adverb
thiamine	Yes	No	No	No
B-complex vitamin	Yes	No	No	No

As nouns, B-complex vitamin is a hypernym of thiamine; that is, B-complex vitamin is a word with a broader meaning than thiamine:

thiamine: a B vitamin that prevents beriberi; maintains appetite and growth
B-complex vitamin: originally thought to be a single vitamin but now separated into several B vitamins

Other hypernyms of thiamine include B, B complex, B vitamin, vitamin B, vitamin B complex.

thiamine (noun)	B-complex vitamin (noun)
a B vitamin that prevents beriberi; maintains appetite and growth	originally thought to be a single vitamin but now separated into several B vitamins