old woman vs woman

old woman and woman both are nouns.

Word	Noun	Adjective	Verb	Adverb
old woman	Yes	No	No	No
woman	Yes	No	No	No

As nouns, woman is a hypernym of old woman; that is, woman is a word with a broader meaning than old woman:

Other hypernyms of old woman include golden ager, old person, oldster, senior citizen, adult female.

old woman (noun)	woman (noun)
a woman who is old	women as a class
herb with greyish leaves found along the east coast of North America; used as an ornamental plant	an adult female person (as opposed to a man)
	a female person who plays a significant role (wife or mistress or girlfriend) in the life of a particular man