upper berth vs upper

upper berth and upper both are nouns.

Word	Noun	Adjective	Verb	Adverb
upper berth	Yes	No	No	No
upper	Yes	Yes	No	No

As nouns, upper berth and upper are synonyms defined as:

upper berth (noun)	upper (noun)
the higher of two berths	piece of leather or synthetic material that forms the part of a shoe or boot above the sole that encases the foot
	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 berth (adjective)	upper (adjective)
	the topmost one of two; upper
	higher in place or position
	superior in rank or accomplishment