Force Spirit
this was the term used to describe any disembodied manifestation of a once-living, Force-sensitive individual. Many Jedi Masters and other strong Force users discovered ways to exist in spirit form, long after their physical body was gone. Rather than simply becoming part of the Force, the denied the will of the Force to retain their individuality. Because this went against the nature of the Force, any Jedi who managed to become a Force Spirit could only manifest itself for a limited time. Because the Sith and other Dark Jedi used the Force for their own ends, they often bypassed this limitation to remain spirits indefinitely. In general, a Force Spirit cannot be "killed" by normal means. Often, as in the case of the Jedi, they simply cease to exist. Other spirits can be destroyed with sufficient Dark Side energy, making the elimination of a malevolent spirit dangerous for most Jedi.