compact disk vs compact disc

compact disk and compact disc both are nouns.

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

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

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

Other synonyms of compact disk include CD.

compact disk (noun)	compact disc (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