In music, a single is a song considered commercially viable enough by the artist and record company to be released separately from an album, usually featuring on an album as well. It is often accompanied by several "B-sides" - usually songs which did not make it onto the album or remixes. See also: 45.

In the UK, a single must meet certain criteria:

  • A maximum of twenty minutes for each single format, including multimedia content
  • A maximum three different tracks for each format
  • Each format must contain the featured song
  • A maximum of 3 different formats (such as CD, DVD, 7" vinyl, 12" vinyl, cassette)

Anything which exceeds these requirements is categorised as an EP or an album.

Further research