saltpetre vs niter

saltpetre and niter both are nouns.

Word	Noun	Adjective	Verb	Adverb
saltpetre	Yes	No	No	No
niter	Yes	No	No	No

As nouns, saltpetre and niter are synonyms defined as:

saltpetre and niter: (KNO3) used especially as a fertilizer and explosive

Other synonyms of saltpetre include nitre, potassium nitrate, saltpeter.

saltpetre (noun)	niter (noun)
(KNO3) used especially as a fertilizer and explosive	(KNO3) used especially as a fertilizer and explosive