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. Usually not exceeding 20 minutes, in the UK it can be released simultaneously on maximum of 3 different formats (such as CD, DVD, 7" vinyl, 12" vinyl, cassette).