Kenneth G. Wilson (1923–). The Columbia Guide to Standard American English. 1993.
disk, disc (nn.)
These were once variant spellings, but American English seems now to have made disk the generic word (the British prefer disc for this purpose), meaning “a flat round object, whether literally a disk, such as a coin, or something that appears disk-shaped, such as the image of the sun.” The bits of cartilage between the vertebrae in the human spine are also disks. Disc then has specialized in American use, meaning particularly “a phonograph record or a compact disc,” but it seems now to be being replaced by disk in most computer-related senses and to be in fading but divided usage as the name of the farmer’s disk [disc] harrow.
