pistil vs carpel

pistil and carpel both are nouns.

Word	Noun	Adjective	Verb	Adverb
pistil	Yes	No	No	No
carpel	Yes	No	No	No

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

pistil: the female ovule-bearing part of a flower composed of ovary and style and stigma
carpel: a simple pistil or one element of a compound pistil

Other hyponyms of pistil include simple pistil, compound pistil, pistillode.

pistil (noun)	carpel (noun)
the female ovule-bearing part of a flower composed of ovary and style and stigma	a simple pistil or one element of a compound pistil