acetic acid vs acetum

acetic acid and acetum both are nouns.

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

As nouns, acetum is a hyponym of acetic acid; that is, acetum is a word with a more specific, narrower meaning than acetic acid:

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

Other hyponyms of acetic acid include trichloracetic acid, trichloroacetic acid, vinegar.

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