A lost episoe of a television series or radio series is one which is, or was at one point, not available for rerun or release on home video or DVD. In some cases, the term is something of a misnomer, used to describe an episode that for any number of reasons was not aired in its original chronological place and later publicly released. It can also refer to episodes that, after their original airing, could not be rerun for various reasons, or episodes that were not, strictly speaking, part of the series, or to episodes which were wiped and no longer exist in an archive.