vitamin A vs retinol

vitamin A and retinol both are nouns.

Word	Noun	Adjective	Verb	Adverb
vitamin A	Yes	No	No	No
retinol	Yes	No	No	No

As nouns, retinol is a hyponym of vitamin A; that is, retinol is a word with a more specific, narrower meaning than vitamin A:

vitamin A: any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes
retinol: an unsaturated alcohol that occurs in marine fish-liver oils and is synthesized biologically from carotene

Other hyponyms of vitamin A include vitamin A1, dehydroretinol, vitamin A2.

vitamin A (noun)	retinol (noun)
any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes	an unsaturated alcohol that occurs in marine fish-liver oils and is synthesized biologically from carotene