upper vs built in bed

upper and built in bed both are nouns.

Word	Noun	Adjective	Verb	Adverb
upper	Yes	Yes	No	No
built in bed	Yes	No	No	No

As nouns, built in bed is a hypernym of upper; that is, built in bed is a word with a broader meaning than upper:

Other hypernyms of upper include berth, bunk.

upper (noun)	built in bed (noun)
piece of leather or synthetic material that forms the part of a shoe or boot above the sole that encases the foot	a bed on a ship or train; usually in tiers
a central nervous system stimulant that increases energy and decreases appetite; used to treat narcolepsy and some forms of depression
the higher of two berths

upper (adjective)	built in bed (adjective)
the topmost one of two; upper
higher in place or position
superior in rank or accomplishment