plant toxin vs nicotine

plant toxin and nicotine both are nouns.

Word	Noun	Adjective	Verb	Adverb
plant toxin	Yes	No	No	No
nicotine	Yes	No	No	No

As nouns, nicotine is a hyponym of plant toxin; that is, nicotine is a word with a more specific, narrower meaning than plant toxin:

plant toxin: any substance produced by plants that is similar in its properties to extracellular bacterial toxin
nicotine: an alkaloid poison that occurs in tobacco; used in medicine and as an insecticide

Other hyponyms of plant toxin include strychnine, brucine, hemlock, mycotoxin, curare, tubocurarine.

plant toxin (noun)	nicotine (noun)
any substance produced by plants that is similar in its properties to extracellular bacterial toxin	an alkaloid poison that occurs in tobacco; used in medicine and as an insecticide