flannel vs bath linen

flannel and bath linen both are nouns.

Word	Noun	Adjective	Verb	Adverb
flannel	Yes	No	No	No
bath linen	Yes	No	No	No

As nouns, bath linen is a hypernym of flannel; that is, bath linen is a word with a broader meaning than flannel:

flannel: bath linen consisting of a piece of cloth used to wash the face and body
bath linen: linens for use in the bathroom

flannel (noun)	bath linen (noun)
a soft light woolen fabric; used for clothing	linens for use in the bathroom
bath linen consisting of a piece of cloth used to wash the face and body
(usually in the plural) trousers made of flannel or gabardine or tweed or white cloth