pressure sore vs ulcer

pressure sore and ulcer both are nouns.

Word	Noun	Adjective	Verb	Adverb
pressure sore	Yes	No	No	No
ulcer	Yes	No	No	No

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

pressure sore: 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 pressure sore include ulceration.

pressure sore (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