gastroscopy vs endoscopy

gastroscopy and endoscopy both are nouns.

Word	Noun	Adjective	Verb	Adverb
gastroscopy	Yes	No	No	No
endoscopy	Yes	No	No	No

As nouns, endoscopy is a hypernym of gastroscopy; that is, endoscopy is a word with a broader meaning than gastroscopy:

gastroscopy: visual examination of the stomach by means of a gastroscope inserted through the esophagus
endoscopy: visual examination of the interior of a hollow body organ by use of an endoscope

gastroscopy (noun)	endoscopy (noun)
visual examination of the stomach by means of a gastroscope inserted through the esophagus	visual examination of the interior of a hollow body organ by use of an endoscope