optical disc vs optical disk

optical disc and optical disk both are nouns.

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

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

optical disc and optical disk: a disk coated with plastic that can store digital data as tiny pits etched in the surface; is read with a laser that scans the surface

optical disc (noun)	optical disk (noun)
a disk coated with plastic that can store digital data as tiny pits etched in the surface; is read with a laser that scans the surface	a disk coated with plastic that can store digital data as tiny pits etched in the surface; is read with a laser that scans the surface