Absence was the state of not being present when expected or simply not existing at all. The Latin phrase in absentia, meaning "in absence," was used in legal settings.
On Omicron Ceti III, the berthold rays would have resulted in the absence of any life on the planet, except that the spores of a certain flowering plant provided protection from them, among other effects. (TOS: "This Side of Paradise")
Prior to at least 2399, artificial life did not exist in Romulan literature, nor did the study of cybernetics. (PIC: "Maps and Legends")
In 2024, Adam Soong told Kore Soong that reality was "a construct of simple-minded fools who can't function in the absence of boundaries." (PIC: "Mercy")
In 2153, T'Pol told the mimetic simbiot Doctor Phlox created to save Commander Trip Tucker's life, Sim, that his absence would affect the crew. (ENT: "Similitude")
In 2154, Koss offered to T'Pol that after their marriage she would only have to stay with him for a year before returning to her work with Starfleet. T'Pol asked if he wanted an absent wife. (ENT: "Home")
In 2161, when T'Pol reflected that she only missed her mother more as time passed despite Commander Tucker telling her the years would make her miss her less, Captain Jonathan Archer observed that "time heals all wounds, but absence makes the heart grow fonder." (ENT: "These Are the Voyages...")
Sometime in the late 2230s or early 2240s, a young Michael Burnham attempted to run away from Sarek's home to spare her foster family being targeted by Logic extremists that might have injured or killed them. When her foster brother Spock tried to follow, she insulted him in an attempt to sever their emotional connection to make her absence less painful. (DIS: "If Memory Serves")
In 2256, when reporting on the Klingons gathered near the edge of Federation space in the Beta Quadrant, Admiral Anderson told Captain Philippa Georgiou to do nothing, absent provocation. (DIS: "The Vulcan Hello")
In December that year, Admiral Katrina Cornwell ordered Captain Gabriel Lorca to stop using the USS Discovery's spore drive unless authorized otherwise by Starfleet. He assured him the rest of the fleet would pick up the slack from their decreased mobility. (DIS: "Choose Your Pain")
In 2257, in the mirror universe, on the ISS Shenzhou, Michael Burnham (assuming the role of her mirror universe counterpart) accuses the crew of having gone soft while she was away. (DIS: "The Wolf Inside")
Reporting on the state of the Federation-Klingon War in 2257, Sarek noted that the Klingon Houses were divided without a clear leader, splitting their united Klingon foes into twenty-four houses. (DIS: "The War Without, The War Within")
Later that year, Spock continued investigating the Red Angel and the associated variance in signal patterns while Michael Burnham was away. (DIS: "The Red Angel")
Also that year, Burnham mused that she wanted to have faith; and that in faith's absence, only duty remained. (DIS: "Saints of Imperfection")
While Captain James T. Kirk was away from the USS Enterprise on Stardate 3219.8 in 2267, Lieutenant Commander Montgomery Scott recorded the ship's log. (TOS: "Metamorphosis")
In 2268, Harry Mudd possessed an android replica of his wife Stella to enjoy her absence. (TOS: "I, Mudd")
That same year, on the planet 892-IV, the runaway slave Flavius had not been in the gladiatorial games for "too long," according to gladiator Maximus. (TOS: "Bread and Circuses")
Also that year, after Ensign Chekov was released from Sickbay after recovering from his reaction to the Tholian web, Lieutenant Commander Spock told him his absence was keenly felt. (TOS: "The Tholian Web")
In 2285, when Captain Kirk requested to take the USS Enterprise back to the Genesis planet, Fleet admiral Morrow informed him that while they were away Project Genesis had become a controversy and so his request was denied. Later in Kirk's apartment, before giving the crew the news, they would toast absent friends. (Star Trek III: The Search for Spock)
In 2364, Commander Tebok attributed Federation expansion to the lack of Romulan attention on matters beyond the Neutral Zone. (TNG: "The Neutral Zone")
In 2365, the USS Enterprise-D encountered a phenomenon that Lieutenant Commander Data characterized as a "hole in space" in which there was no matter or energy and that, by any accepted standard, did not exist. The lack of information made it difficult for him to assess what it was or what effect it could have. (TNG: "Where Silence Has Lease")
Later that year, when the USS Enterprise-D was searching for the IKS Pagh to warn them of organisms damaging the hull, Lieutenant Commander Data deduced it was cloaked since they detected no debris. (TNG: "A Matter Of Honor")
Later the same year, Counselor Deanna Troi expressed concern for Lieutenant Geordi La Forge while he was away assisting the Pakled ship Mondor. (TNG: "Samaritan Snare")
When participating in a battle simulation that year, Commander Riker assumed command of the USS Hathaway. Lieutenant Commander Data served as first officer aboard the USS Enterprise-D while he was away. (TNG: "Peak Performance")
In 2366, after the accidental death of Marla Aster, Commander Data admitted he did not "sense the same feelings of absence" he had after the death of Lieutenant Natasha Yar in 2364. Riker explained it was "human nature" to experience loss more intensely with a close relationship. (TNG: "The Bonding")
Later that year, the USS Enterprise-D gave a concert in honor of Ambassador Sarek. It continued even though he was unable to attend. (TNG: "Sarek")
In 2367, Doctor Dalen Quaice told Doctor Beverly Crusher that his wife's absence after her death was distracting. (TNG: "Remember Me")
When explaining his "feeling" of friendship in 2367, Data described the sense of familiarity: experiencing sensory inputs to which his mental pathways would become accustomed, anticipating those inputs, and missing them when they did not occur. (TNG: "Legacy") The next year, Troi reminded Riker of Data's definition of friendship when they discovered his severed head in a cavern on Earth among artifacts from the nineteenth century. (TNG: "Time's Arrow")
When Hannah Bates prepared to temporarily leave the colony on Moab IV in 2368, Martin Benbeck was concerned that her absence further imbalance the colony. (TNG: "The Masterpiece Society")
When Odo was removed from his position in security on Deep Space 9 in 2369 due to being under investigation for murder, he told Quark to take advantage of his absence. (DS9: "A Man Alone")
Later that year, during an investigation of General Ardelon Tandro's death in 2339, Odo proposed a theory that Curzon Dax and the general's wife, Enina, had an affair. He wasn't sure whether Dax had been innocently comforting Enina in while the general was away fighting or if he'd purposefully taken advantage of the general's absence, but considered either a motive for murder. (DS9: "Dax")
The same year, the fugitive Croden was declared guilty in absentia for myriad crimes on Rakhar. (DS9: "Vortex")
When Kahless appeared to be discovered alive later that year, Data asked Lieutenant Worf how he would determine whether he was "the real Kahless" without empirical data. (TNG: "Rightful Heir")
In 2370, while Data was missing on Barkon IV, Counselor Troi was promoted to commander. (TNG: "Thine Own Self")
In 2371, while The Doctor was preparing to investigate photonic energy readings and the disappearance of crewmates on the holodeck, he told Kes to continue her studies by learning how to operate the base pair sequencer while he was gone. (VOY: "Heroes and Demons")
In 2372, when Keiko O'Brien was on an agrobiology expedition on Bajor for six months, Chief Miles O'Brien set up a little workshop in the bedroom. He saw it as spending his free time in a place he associated with Keiko, thereby expressing a desire to be closer to her while she was away. (DS9: "Hippocratic Oath")
Also that year, when Commander Chakotay went missing while performing the pakra for his father's death, Captain Kathryn Janeway decided to continue to investigate as if Chakotay was still alive until they found evidence otherwise. (VOY: "Initiations")
That same year, when Q intruded upon his privacy, Lieutenant Tuvok wondered if an absence of manners was always a feature of the Q, or whether it was due to the species' evolutionary process resulting from omnipotence. (VOY: "Death Wish")
Also as of 2372, USS Voyager's protocols allowed Commander Chakotay to assume the place of the captain when Janeway was not available. (VOY: "Persistence of Vision")
When Chief O'Brien was away from the station in 2374, Major Kira Nerys noted that the station always experienced system glitches when he was away. (DS9: "Honor Among Thieves")
Also that year, Janeway took part in a holoprogram regarding Leonardo da Vinci's Great Bird invention. Da Vinci was reluctant to resume testing it, since the river Arno that had saved them before had dried up, and they would crash in the rocks if the flight failed. (VOY: "Concerning Flight")
Later that year, The Doctor informed Janeway that he had been developing a psychiatric subroutine to act as ship's counselor, as the USS Voyager had none. (VOY: "Retrospect")
Later the same year, while the USS Voyager was under Hirogen control, forcing the crew to play the parts of various holodeck characters, Tuvok told Janeway (playing Katrine) that he might be forced to decide whether Seven of Nine (playing Mademoiselle de Neuf) was on their side for himself. (VOY: "The Killing Game")
When encountering the Omega molecule later that year, Janeway informed the crew that because they were so far away from Starfleet Command, they would have to contain the threat themselves. (VOY: "The Omega Directive")
In 2375, Kor offered the toast "to absent comrades" while drinking bloodwine with Worf in honor of Jadzia Dax. (DS9: "Once More Unto the Breach")
Also that year, when Seven of Nine was possessed by multiple neural patterns of individuals previously assimilated by the Borg, she herself was "absent" while they assumed control of her body. (VOY: "Infinite Regress")
Later that year, Captain Janeway ordered Seven of Nine to take charge of Engineering while B'Elanna Torres was in Sickbay. (VOY: "Nothing Human")
In 2376, when attempting to convince The Doctor to remain on the Qomar homeworld, Tincoo told him that the crew was resourceful and would be able to compensate for his absence. (VOY: "Virtuoso")
Later that year, while the chief of mining operations on Telsius was away in the Grenna system, he authorized two other miners to make trades. (VOY: "Live Fast and Prosper")
In 2377, when Mezoti, Rebi, and Azan were leaving the USS Voyager to stay with the Wysanti, Mezoti told Icheb, who would remain, that it would be difficult to adapt to his absence. (VOY: "Imperfection")
Later that year, when searching the planet Quarra for the crew, Chakotay told The Doctor and Ensign Harry Kim to "work out" who would be in charge while he was away. (VOY: "Workforce")
That same year, Seven of Nine personally delivered a gift of baby booties to B'Elanna Torres for her baby shower, since she was unable to attend. (VOY: "Human Error")
In 2379, on board the USS Enterprise-E after the destruction of the Scimitar in the Bassen Rift, Captain Picard made the toast to absent friends and family in honor of Data. (Star Trek Nemesis)
In 2380, while Captain Carol Freeman, Commander Jack Ransom, and a team went to the Pisepian agricultural colony, the USS Cerritos received a temporary transfer of command to a visiting captain in their absence. (LD: "Much Ado About Boimler")
Also in the late 24th century, according to Commander Kassia Nox, Starbase 80's lack of food replicators livened the station's culinary scene with food vendors. (LD: "Starbase 80?!")
In 2384, Admiral Janeway insisted that the kids were heroes, not criminals, and she would not tolerate them being denigrated. She also said, "In their absence, and in my presence, they get our respect." (PRO: "Supernova, Part 2")
In 2401, when discussing the Borg's goals and shifting tactics: deception in absence of strength for the attainment of victory at any cost. (PIC: "The Star Gazer")
Later that year, after Riker and Troi escaped a holding cell on the Changeling ship Shrike to download the database, their absence was discovered just as they completed the download. (PIC: "Surrender")
Shortly after, Picard stood in a desolate Borg cube and mused what else could they do but raise another army in absence of the dead one on the cube. (PIC: "The Last Generation")
In 3189, after crash landing on a planet, Saru informs the remaining bridge crew they will not share any of their knowledge of the past, adhere to local standards, and trade in peace, regardless of Philippa Georgiou's objections. (DIS: "Far From Home")
Later that year, Captain Saru hoped Lieutenant jg Tilly could explain Michael Burnham's absence. He would later assure Admiral Charles Vance that would not impact the USS Discovery's ability to respond to potential problems. (DIS: "Scavengers")
Later, Admiral Vance offered his condolences for the loss of Philippa Georgiou, knowing he would feel her absense. (DIS: "Terra Firma, Part 2")
Later the same year, the holographic elder that attended Su'Kal was evidence that the program was degrading. (DIS: "That Hope Is You, Part 2")
In 3190, after having been reinstated to Starfleet, Saru continued to serve as a council member in absentia in his village. (DIS: "Anomaly (DIS)")