A starship is a manned transport vessel capable of interstellar flight. The term has been used in many science fiction vehicles, but is most popularly attributed to the Star Trek mythos. Starships serve a variety of functions and may be deployed as military vessels, exploratory/research vessels or medical frigates. Some starships may even be sleeper ships or generational ships. Starships generally use propulsion systems that provide them with faster-than-light (FTL) capabilities, often times using warp technology to bridge vast distances in a relatively shortened period of time.