B vitamin vs B complex

B vitamin and B complex both are nouns.

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

As nouns, B vitamin and B complex are synonyms defined as:

B vitamin and B complex: originally thought to be a single vitamin but now separated into several B vitamins

Other synonyms of B vitamin include B-complex vitamin, B, vitamin B, vitamin B complex.

B vitamin (noun)	B complex (noun)
originally thought to be a single vitamin but now separated into several B vitamins	originally thought to be a single vitamin but now separated into several B vitamins