喂鸡百科说的:
An extended play (EP) is a musical recording that contains more music than a
single, but is too short to qualify as a full studio album or LP. The term
EP originally referred to specific types of vinyl records other than 78 rpm
standard play (SP) records and LP records, but it is now applied to mid-
length Compact Discs and music downloads as well. Ricardo Baca of The Denver
Post said, "EPs—originally extended-play 'single' releases that are
shorter than traditional albums—have long been popular with punk and indie
bands." In the United Kingdom, the Official Chart Company defines a boundary
between EP and album classification at 25 minutes of length or four tracks
(not counting alternative versions of featured songs, if present).