Tetryon
A tetryon was a subatomic particle that can only exist in subspace environments. Tetryon radiation is a bombardment of these particles. Since these particles are a property of subspace, they become highly energetic and unstable when they are extruded into normal space, which can occur by both natural and artificial means. Tetryons have a random momentum, and thus cannot be tracked by sensors. 

In 2369, solanogen-based lifeforms from a tertiary subspace manifold used a stream of spatially inverted tetryons to open a spatial rupture between their native realm and the . This allowed them to abduct several Enterprise crew members for experimentation. ()

Later that year, Dr. Beverly Crusher investigated the death of Dr. Reyga, a Ferengi scientist. Jo'Bril, a Takaran scientist who piloted the Justman into the star Veytan to test Reyga's metaphasic shield, was supposedly killed after the Justmans shields failed. Crusher wanted to know if Jo'Bril was exposed to a tetryon field inside the shuttle, as it would have left residual traces in his system. Crusher did find traces of tetryons in his system, convincing her that someone sabotaged the shields on the shuttle. ()

Intense tetryon fields, such as those surrounding the Hekaras Corridor, pose a hazard to spacecraft. ()

Bombardment with tetryons can render directed-energy weapons inoperative. Jadzia Dax utilized tetryons to disable the weapons of The Albino's troops on Secarus IV in 2370. ()

In 2370, Odo theorized that a weapon used by Trazko to shoot Quark was tetryon-based, to avoid activating the weapon detection scanners on the Promenade of Deep Space 9. Doctor Bashir noted that this was consistent with Quark's injuries. ()

The  used a coherent tetryon beam to scan starships before dragging them to the Delta Quadrant with a displacement wave. ()

In 2371, Jadzia Dax scanned the area around Deep Space 9 and did not find anything at first. However, after scanning on a lower subspace bandwidth, she discovered low-level tetryon emissions. This was discovered to be a quantum singularity. ()

Later on, Commander Benjamin Sisko informed Chief Miles O'Brien that sensors had discovered high concentrations of tetryon particles moving towards Deep Space 9. Suddenly, a Cardassian  ship decloaked and went into the Bajoran wormhole heading for the Gamma Quadrant. ()

Later that year, Dax found a sabotage device located in a warp plasma conduit on the . In trying to find out who the saboteur was, Dax said that whoever committed the sabotage would have been exposed to trace elements of tetryon particles. ()

In an alternate timeline, Harry Kim and Tom Paris stole the  runabout  and had a  vessel on their tail. Kim was able to elude them for a short time by venting tetryon plasma from the Yellowstones nacelles. The tetryon plasma emitted multiflux gamma radiation, which disrupts subspace. The plan was successful in stalling the Nebula-class vessel's engines. () 

In 2372, tetryon pulse echoes were used to navigate the highly unstable atmosphere of a gas giant. However, course modifications were required after each pulse in order to avoid detection. This meant that the random momentum to avoid being tracked by sensors was invalid when emitted as a pulse. ()

In 2373, the infant Changeling given to Odo by Quark was suffering from exposure tetryon radiation. ()

Later that year, Harry Kim detected a tetryon surge from a Nasari ship and interpreted it as a sign they were about to attack, due to a "hunch" caused by his exposure to a Taresian retrovirus. He was later found to be right, as Nasari particle beam weapons are tetryon-based. ()

Later that year,  traveled through a region of heavy tetryon radiation. Lieutenant Tuvok enhanced the ship's shields to compensate. ()

The atmosphere inside a Borg cube contains tetryon particles. ()

In 2375, Captain Jean-Luc Picard took several weapons with him from the  before leaving for the Ba'ku planet to fight the forced relocation of the Ba'ku, including seven metric tons of ultritium explosives, eight tetryon pulse launchers and ten isomagnetic disintegrators. ()

The weapons of Qatai's vessel were tetryon-based. In 2375, Qatai used them to initiate an electrolytic reaction in a burst of antimatter ejected from Voyagers nacelles. This caused the telepathic pitcher plant to regurgitate both ships. ()

The Nacene generated power with the use of tetryons. ()

In 2377, Voyager struck a subspace mine. This lead to the ship being flooded with tetryon radiation, and most of the crew suffering radiation poisoning as a result. With The Doctor only able to stabilize the condition of the crew at best until the radiation could be purged, Captain Janeway was forced to order the ship abandoned. Before leaving, Janeway left The Doctor, as the Emergency Command Hologram, in command of Voyager. The Doctor was eventually able to vent the radiation. ()

The energy barrier that isolates the territory of the Ventu on Ledos has a distinct tetryon signature. The Borg had previously encountered the technology in Species 312. The barrier left a distinct tetryon flux on debris from a Voyager shuttlecraft that crashed into it in 2378. Seven of Nine was able to construct a tetryon-based signaling device to open the energy barrier briefly from the remains of a Class 2 shuttle. ()

Tetryon weapons
 Compressed tetryon beam weapon
 Tetryon pulse launcher

Tetryon applications
 Tetryon plasma
 Coherent tetryon beam
 Tetryon compositor
 Tetryon reactor
 Tetryon power cell
 Tetryon-based signaling device

Apocrypha
In the game Star Trek Online, tetryon-based energy weapons were available to characters of rank commander and higher. Their special ability was a 2.5% chance to inflict additional shield damage. They were depicted in the game appearing as azure blue energy.

de:Tetryon
ja:テトリオン
Subspace
Particles