alkali vs pyridine

alkali and pyridine both are nouns.

Word	Noun	Adjective	Verb	Adverb
alkali	Yes	No	No	No
pyridine	Yes	No	No	No

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

alkali: any of various water-soluble compounds capable of turning litmus blue and reacting with an acid to form a salt and water
pyridine: a toxic colorless flammable liquid organic base with a disagreeable odor; usually derived from coal

Other hyponyms of alkali include purine, purine, glyoxaline, imidazole, iminazole, cyanuramide, melamine, pyrimidine.

alkali (noun)	pyridine (noun)
any of various water-soluble compounds capable of turning litmus blue and reacting with an acid to form a salt and water	a toxic colorless flammable liquid organic base with a disagreeable odor; usually derived from coal
a mixture of soluble salts found in arid soils and some bodies of water; detrimental to agriculture