sigmoidoscopy vs endoscopy

sigmoidoscopy and endoscopy both are nouns.

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

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

sigmoidoscopy: visual examination (with a sigmoidoscope) of the lower third of the colon in a search for polyps
endoscopy: visual examination of the interior of a hollow body organ by use of an endoscope

sigmoidoscopy (noun)	endoscopy (noun)
visual examination (with a sigmoidoscope) of the lower third of the colon in a search for polyps	visual examination of the interior of a hollow body organ by use of an endoscope