lumber room vs stowage

lumber room and stowage both are nouns.

Word	Noun	Adjective	Verb	Adverb
lumber room	Yes	No	No	No
stowage	Yes	No	No	No

As nouns, stowage is a hypernym of lumber room; that is, stowage is a word with a broader meaning than lumber room:

lumber room: a storeroom in a house where odds and ends can be stored (especially furniture)
stowage: a room in which things are stored

Other hypernyms of lumber room include storage room, storeroom.

lumber room (noun)	stowage (noun)
a storeroom in a house where odds and ends can be stored (especially furniture)	the act of packing or storing away
	a room in which things are stored
	the charge for stowing goods