stomach ache vs gastralgia

stomach ache and gastralgia both are nouns.

Word	Noun	Adjective	Verb	Adverb
stomach ache	Yes	No	No	No
gastralgia	Yes	No	No	No

As nouns, stomach ache and gastralgia are synonyms defined as:

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

Other synonyms of stomach ache include bellyache, stomachache.

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