soda water vs seltzer

soda water and seltzer both are nouns.

Word	Noun	Adjective	Verb	Adverb
soda water	Yes	No	No	No
seltzer	Yes	No	No	No

As nouns, soda water and seltzer are synonyms defined as:

soda water and seltzer: effervescent beverage artificially charged with carbon dioxide

Other synonyms of soda water include carbonated water, club soda, sparkling water.

soda water (noun)	seltzer (noun)
effervescent beverage artificially charged with carbon dioxide	naturally effervescent mineral water
a sweet drink containing carbonated water and flavoring	effervescent beverage artificially charged with carbon dioxide