CD vs compact disk

CD and compact disk both are nouns.

Word	Noun	Adjective	Verb	Adverb
CD	Yes	No	No	No
compact disk	Yes	No	No	No

As nouns, CD and compact disk are synonyms defined as:

CD and compact disk: a digitally encoded recording on an optical disk that is smaller than a phonograph record; played back by a laser

Other synonyms of CD include compact disc.

CD (noun)	compact disk (noun)
a digitally encoded recording on an optical disk that is smaller than a phonograph record; played back by a laser	a digitally encoded recording on an optical disk that is smaller than a phonograph record; played back by a laser
a debt instrument issued by a bank; usually pays interest