audio CD vs compact disc

audio CD and compact disc both are nouns.

Word	Noun	Adjective	Verb	Adverb
audio CD	Yes	No	No	No
compact disc	Yes	No	No	No

As nouns, compact disc is a hypernym of audio CD; that is, compact disc is a word with a broader meaning than audio CD:

audio CD: compact discs used to reproduce sound (voice and music)
compact disc: a digitally encoded recording on an optical disk that is smaller than a phonograph record; played back by a laser

Other hypernyms of audio CD include CD, compact disk.

audio CD (noun)	compact disc (noun)
compact discs used to reproduce sound (voice and music)	a digitally encoded recording on an optical disk that is smaller than a phonograph record; played back by a laser