bedsore vs ulcer

bedsore and ulcer both are nouns.

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

As nouns, ulcer is a hypernym of bedsore; that is, ulcer is a word with a broader meaning than bedsore:

bedsore: a chronic ulcer of the skin caused by prolonged pressure on it (as in bedridden patients)
ulcer: a circumscribed inflammatory and often suppurating lesion on the skin or an internal mucous surface resulting in necrosis of tissue

Other hypernyms of bedsore include ulceration.

bedsore (noun)	ulcer (noun)
a chronic ulcer of the skin caused by prolonged pressure on it (as in bedridden patients)	a circumscribed inflammatory and often suppurating lesion on the skin or an internal mucous surface resulting in necrosis of tissue