stowage vs lumber room

stowage and lumber room both are nouns.

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

As nouns, lumber room is a hyponym of stowage; that is, lumber room is a word with a more specific, narrower meaning than stowage:

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

Other hyponyms of stowage include chandlery, buttery, larder, pantry, stock room, stockroom, strongroom.

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