melamine vs alkali

melamine and alkali both are nouns.

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

As nouns, alkali is a hypernym of melamine; that is, alkali is a word with a broader meaning than melamine:

melamine: a white crystalline organic base; used mainly in making melamine resins
alkali: any of various water-soluble compounds capable of turning litmus blue and reacting with an acid to form a salt and water

Other hypernyms of melamine include base.

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