A disk or disc is anything that resembles a flattened cylinder in shape. More specifically:

• In biology, an intervertebral disc is a cartilaginous joint between vertebrae in the spine of vertebrate animals.
• In mathematics, a disk is a geometrical object. See Disk (mathematics).
• A gramophone record (commonly "phonograph record" in U.S. English) is an analogue sound recording disc used on a gramophone or phonograph. It consists of a long spiral groove in on a side of a platter, commonly of vinyl, shellac or lacquer.
• The hard disk and floppy disk are magnetic storage media used in computers.
• A variety of optical storage media, such as the compact disc, DVD, and laserdisc, are used for digital data or video.
• Disc brakes are often used in automobiles.
• In astrophysics, an accretion disc or disk is a structure formed by material falling into a gravitational source.
• The Frisbee is a flying disc toy.

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.

See also

• Astrophysics
  • Accretion disc
  • Protoplanetary disc
  • Scattered disk object
• Audio and Video
  • Blu-ray Disc
  • Compact disc
  • DVD
  • HD-DVD
  • Laserdisc
  • MiniDisc
  • Nipkow disk
• Biology
  • Discus (fish)
  • Intervertebral disc
• Computing
  • Disk storage
  • Floppy disk
  • Hard disk
  • RAM disk
• Discus throw
• Disco
• Mathematics
  • Disk (mathematics)
  • Euler's disk
  • Unit disc

External links

• Usage note from American Heritage Dictionary (http://www.bartleby.com/61/16/C0521600.html)

da:Disk fr:Disque ja:ディスク