sterol vs ergosterol

sterol and ergosterol both are nouns.

Word	Noun	Adjective	Verb	Adverb
sterol	Yes	No	No	No
ergosterol	Yes	No	No	No

As nouns, ergosterol is a hyponym of sterol; that is, ergosterol is a word with a more specific, narrower meaning than sterol:

sterol: any of a group of natural steroid alcohols derived from plants or animals; they are waxy insoluble substances
ergosterol: a plant sterol that is converted into vitamin D by ultraviolet radiation

Other hyponyms of sterol include cholesterin, cholesterol, mycosterol.

sterol (noun)	ergosterol (noun)
any of a group of natural steroid alcohols derived from plants or animals; they are waxy insoluble substances	a plant sterol that is converted into vitamin D by ultraviolet radiation