lass vs young woman

lass and young woman both are nouns.

Word	Noun	Adjective	Verb	Adverb
lass	Yes	No	No	No
young woman	Yes	No	No	No

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

Other hypernyms of lass include fille, girl, miss, missy, young lady.

lass (noun)	young woman (noun)
a girl or young woman who is unmarried	a young female