thiamin vs B vitamin

thiamin and B vitamin both are nouns.

Word	Noun	Adjective	Verb	Adverb
thiamin	Yes	No	No	No
B vitamin	Yes	No	No	No

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

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

Other hypernyms of thiamin include B-complex vitamin, B, B complex, vitamin B, vitamin B complex.

thiamin (noun)	B 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