In television, an episode is a single event of a series. The time varies depending on the nature of the series, but most are between fifteen and fifty minutes long (excluding commercial breaks). Episodes can be both self-contained (a completed story from beginning to end) or serial (a continuation of a previous or future story). There is some confusion when programs run episodes for an unusual length of time; for example by airing a two-hour episode of a show that is normally only one hour. Some people consider this to be two separate (though linked) episodes while others consider it to be a single episode.