nicotine vs alkaloid

nicotine and alkaloid both are nouns.

Word	Noun	Adjective	Verb	Adverb
nicotine	Yes	No	No	No
alkaloid	Yes	No	No	No

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

nicotine: an alkaloid poison that occurs in tobacco; used in medicine and as an insecticide
alkaloid: natural bases containing nitrogen found in plants

Other hypernyms of nicotine include pressor, vasoconstrictive, vasoconstrictor, phytotoxin, plant toxin.

nicotine (noun)	alkaloid (noun)
an alkaloid poison that occurs in tobacco; used in medicine and as an insecticide	natural bases containing nitrogen found in plants