B-side

• a different version (e.g., instrumental, live, acoustic,remixed version orin another language/text) of the A-side or another track
• another song from the same album, which the record company does not want to release on its own
• a song not considered good enough for the album
• a song that had not yet been completed at the time of the album's release
• a song that was intended to be B-side after all
• in concept records: a song that doesn't fit into the story line. (1)

(1) Wikipedia contributors, 'A-side and B-side', Wikipedia, The Free Encyclopedia, 27 July 2008, 08:18 UTC, <http://en.wikipedia.org/w/index.php?title=A-side_and_B-side&oldid=228155109> [accessed 30 July 2008]