nicotine vs plant toxin

nicotine and plant toxin both are nouns.

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

As nouns, plant toxin is a hypernym of nicotine; that is, plant toxin is a word with a broader meaning than nicotine:

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

Other hypernyms of nicotine include pressor, vasoconstrictive, vasoconstrictor, alkaloid, phytotoxin.

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