(covers information from several alternate timelines)
- For other meanings of "Lifesigns", please see Lifesigns (disambiguation).
A life sign or bio-sign is a signal or collection of signals given off by a lifeform that indicates that it is currently alive, or functional. Upon approaching another starship or a planet for which they had limited intelligence, starships usually performed a scan for life signs. This information became part of the bridge crew's determination as to whether to board the ship, send a landing party, or carry out any other action.