saltpeter vs potassium nitrate

saltpeter and potassium nitrate both are nouns.

Word	Noun	Adjective	Verb	Adverb
saltpeter	Yes	No	No	No
potassium nitrate	Yes	No	No	No

As nouns, saltpeter and potassium nitrate are synonyms defined as:

saltpeter and potassium nitrate: (KNO3) used especially as a fertilizer and explosive

Other synonyms of saltpeter include niter, nitre, saltpetre.

saltpeter (noun)	potassium nitrate (noun)
(KNO3) used especially as a fertilizer and explosive	(KNO3) used especially as a fertilizer and explosive