A ghost from "A Christmas Carol"
"Spirits, souls. My people used to call them Borhyas. Whatever term you want to use, we're it."
"But my uniform, my VISOR. Are you saying I'm some blind ghost with clothes?"
"I don't have all the answers. I've never been dead before."
A ghost, or phantom, was a purported spirit of a dead individual. A tale of such spirits was called a ghost story. In the Bajoran language, the relative term was Borhyas. (TNG: "The Next Phase")
When Trip Tucker called the Terra Nova colony a "ghost town", Captain Jonathan Archer answered, "Let's hope the ghosts can give us some answers." (ENT: "Terra Nova")
The Kzinti had legends of weapons being haunted by their dead owners. (TAS: "The Slaver Weapon")
In 2257, Christopher Pike told his first officer, Una Chin-Riley, that he always thought holographic transmissions looked too much like ghosts. (DIS: "An Obol for Charon")
In 2268 the Amerind inhabitants believed that a temple spirit occupied the Preservers' obelisk on their planet. (TOS: "The Paradise Syndrome")
Later that year, after James T. Kirk suggested that the Kalandan outpost was a ghost planet, Doctor Leonard McCoy stated that the mysterious woman they had encountered there almost made a ghost out of Hikaru Sulu. (TOS: "That Which Survives")
In 2287, Kirk commented that Spock looks like he's just seen a ghost, when the latter saw the image of his half-brother, Sybok. (Star Trek V: The Final Frontier)
In 2364, Felix Leech believed the pale Data looked like a ghost. (TNG: "The Big Goodbye")
Later that year, Beverly Crusher described Jenice Manheim as a ghost from Jean-Luc Picard's past. (TNG: "We'll Always Have Paris")
In 2365, Ensign Nagel claiming that the Kreechta was not a ghost attacking the USS Enterprise-D. TNG: "Peak Performance")
In 2366, William Riker believed the Enterprise crew were being asked to chase ghosts, given the supposed impossibility of Humans being able to survive on Tau Cygna V. (TNG: "The Ensigns of Command")
In an alternate timeline later that year, Picard described the USS Enterprise-C as "a ghost from [the Enterprise-D's] own past." (TNG: "Yesterday's Enterprise")
In 2367, before it was discovered what the two-dimensional beings really were, Commander William T. Riker referred to them as ghosts and said he didn't want to be tailed by them all the way to T'lli Beta. (TNG: "The Loss")
For a moment, the Ux-Mal criminals on Mab-Bu VI appeared to the crew of the Enterprise as ghosts or spirits, that took control over the body of the living. Worf stated that the Klingon name for such a spirit was "jat'yIn". (TNG: "Power Play")
Some lifeforms are so alien that they can appear ghost-like. Anaphasic lifeforms are long-lived entities that can only appear corporeal when attached to a particular object, or a person with an unusual biochemistry. The females of the Howard family were host to an anaphasic lifeform, who posed as the ghost of a 17th century Scotsman named Ronin, for centuries. (TNG: "Sub Rosa")
See also: Non-corporeal species.
Many species believed that part of a person lives on after death; examples include the Bajoran pagh or the Ocampa comra. These beliefs were often found in religion. (DS9: "Emissary", "In the Hands of the Prophets"; VOY: "Emanations") Deanna Troi once sensed that the Devidians, in the form the crew of the Enterprise-D found them, had died in terror and she sensed an echo of life, though they still required sustenance thereafter. (TNG: "Time's Arrow", "Time's Arrow, Part II")
While searching for information about the creators of the aphasia virus, Kira Nerys believed she was searching for ghosts when she learned that one of the virus' creators, Dekon Elig, had died on stardate 39355. (DS9: "Babel")
In many legends, ghosts have the ability to appear and disappear at will. In 1944 of an alternate timeline created by the Temporal Cold War going hot, Jonathan Archer and Alicia Travers, about to be captured by a Nazi-Na'kuhl alliance, were brought aboard Enterprise via transporter, a technology almost incomprehensible to Humans of that time. After Alicia's return to Earth, Carmine told her of a rumor he had heard – that, after being cornered by the enemy, she and Archer had vanished into thin air, "like ghosts." (ENT: "Storm Front, Part II")
Commander Sisko said, ironically, that Rao Vantika must have had an accomplice who did the system breakdown because two bodies found on the Reyab were in the station's morgue, and he ruled out the possibility that Vantika's ghost was wandering through Deep Space 9's halls. (DS9: "The Passenger")
The term "ghost" can also mean a false image or shadow of an image, as in a sensor ghost. (DS9: "Soldiers of the Empire")
After Jadzia Dax saw Quark's hologram of the apparently deceased Morn, the Ferengi told her that it looked as if she had "seen a ghost." (DS9: "Who Mourns for Morn?")
Manifestations of Quinn Erickson's disembodied transporter signal haunted ships that entered a region of space known as The Barrens. (ENT: "Daedalus")
The term "ghost" was referenced in the final draft script of TOS: "Miri"; describing an upset Janice Rand regaining her composure, the teleplay referred to her as "forcing the ghost of her old flipness."