record sleeve vs record cover

record sleeve and record cover both are nouns.

Word	Noun	Adjective	Verb	Adverb
record sleeve	Yes	No	No	No
record cover	Yes	No	No	No

As nouns, record sleeve and record cover are synonyms defined as:

record sleeve and record cover: a sleeve for storing a phonograph record

record sleeve (noun)	record cover (noun)
a sleeve for storing a phonograph record	a sleeve for storing a phonograph record