acetum vs acetic acid

acetum and acetic acid both are nouns.

Word	Noun	Adjective	Verb	Adverb
acetum	Yes	No	No	No
acetic acid	Yes	No	No	No

As nouns, acetic acid is a hypernym of acetum; that is, acetic acid is a word with a broader meaning than acetum:

acetum: a dilute solution of acetic acid that is used as a solvent (e.g. for a drug)
acetic acid: a colorless pungent liquid widely used in manufacturing plastics and pharmaceuticals

Other hypernyms of acetum include ethanoic acid.

acetum (noun)	acetic acid (noun)
sour-tasting liquid produced usually by oxidation of the alcohol in wine or cider and used as a condiment or food preservative	a colorless pungent liquid widely used in manufacturing plastics and pharmaceuticals
a dilute solution of acetic acid that is used as a solvent (e.g. for a drug)