stomachache vs gastralgia

stomachache and gastralgia both are nouns.

Word	Noun	Adjective	Verb	Adverb
stomachache	Yes	No	No	No
gastralgia	Yes	No	No	No

As nouns, stomachache and gastralgia are synonyms defined as:

stomachache and gastralgia: an ache localized in the stomach or abdominal region

Other synonyms of stomachache include bellyache, stomach ache.

stomachache (noun)	gastralgia (noun)
an ache localized in the stomach or abdominal region	an ache localized in the stomach or abdominal region