upper vs upper berth

upper and upper berth both are nouns.

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

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

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