A disk or disc is anything that resembles a flattened cylinder in shape. More specifically:
Disk or disc?
The divergence in spelling is due in part to the way in which the words originated. Disk came into the English language in the mid-17th century, and was modelled on words such as whisk; disc arose some time later, and was based on the original Latin root discus. In the 19th century, disc became the conventional spelling for audio recordings made on a flat plate, such as the gramophone record; this usage gave rise to the modern term disc jockey. Early BBC technicians differentiated between disks (in-house transcription records) and discs (the colloquial term for commercial gramophone records, or what the BBC dubbed CGRs).
By the 20th century, the c-spelling was more popular in British English, while the k-spelling was preferred in American English. In the 1940s, when the American company IBM pioneered the first hard disk storage devices, the k-spelling was used. In 1979 the European company Philips, along with Sony, developed the compact disc medium; here, the c-spelling was chosen, possibly because of the predominating British spelling, or because the compact disc was seen as a successor to the analogue disc record.
Whatever their heritage, in computer jargon today it is common for the k-spelling to refer mainly to magnetic storage devices, while the c-spelling is customary for optical media such as the compact disc and similar technologies. Even in the computing field, however, the terms are used inconsistently; software documentation often uses the k-spelling exclusively.
Etymology: from Greek δίσκος, a flat round object athletes competed in throwing. See discus throw.
- Usage note from American Heritage Dictionary (http://www.bartleby.com/61/16/C0521600.html)