Compact disc and Optical disk

Compact disc noun - A digitally encoded recording on an optical disk that is smaller than a phonograph record; played back by a laser.

Optical disk and compact disc are semantically related. In some cases you can use "Optical disk" instead a noun phrase "Compact disc".

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.

Compact disc and optical disk are semantically related. Sometimes you can replace phrase "Compact disc" with "Optical disk", this phrases are similar.