lower vs built in bed

lower and built in bed both are nouns.

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

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

Other hypernyms of lower include berth, bunk.

lower (noun)	built in bed (noun)
the lower of two berths	a bed on a ship or train; usually in tiers

lower (adjective)	built in bed (adjective)
the bottom one of two

lower (verb)	built in bed (verb)
make lower or quieter
set lower
cause to drop or sink
move something or somebody to a lower position
look angry or sullen, wrinkle one's forehead, as if to signal disapproval