potassium alum vs Al

potassium alum and Al both are nouns.

Word	Noun	Adjective	Verb	Adverb
potassium alum	Yes	No	No	No
Al	Yes	No	No	No

As nouns, Al is a hypernym of potassium alum; that is, Al is a word with a broader meaning than potassium alum:

potassium alum: a white crystalline double sulfate of aluminum: the potassium double sulfate of aluminum
Al: a silvery ductile metallic element found primarily in bauxite

Other hypernyms of potassium alum include aluminium, aluminum, atomic number 13, double salt.

potassium alum (noun)	Al (noun)
a white crystalline double sulfate of aluminum: the potassium double sulfate of aluminum	a silvery ductile metallic element found primarily in bauxite