ulcer vs peptic ulcer

ulcer and peptic ulcer both are nouns.

Word	Noun	Adjective	Verb	Adverb
ulcer	Yes	No	No	No
peptic ulcer	Yes	No	No	No

As nouns, peptic ulcer is a hyponym of ulcer; that is, peptic ulcer is a word with a more specific, narrower meaning than ulcer:

ulcer: a circumscribed inflammatory and often suppurating lesion on the skin or an internal mucous surface resulting in necrosis of tissue
peptic ulcer: an ulcer of the mucous membrane lining of the alimentary tract

ulcer (noun)	peptic ulcer (noun)
a circumscribed inflammatory and often suppurating lesion on the skin or an internal mucous surface resulting in necrosis of tissue	an ulcer of the mucous membrane lining of the alimentary tract