alkali vs melamine

alkali and melamine both are nouns.

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

As nouns, melamine is a hyponym of alkali; that is, melamine 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
melamine: a white crystalline organic base; used mainly in making melamine resins

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

alkali (noun)	melamine (noun)
any of various water-soluble compounds capable of turning litmus blue and reacting with an acid to form a salt and water	a white crystalline organic base; used mainly in making melamine resins
a mixture of soluble salts found in arid soils and some bodies of water; detrimental to agriculture