In the fictional Star Trek universe, the Trill are a race of symbiotic lifeforms native to the Alpha Quadrant.

The hosts, as they are called, are a humanoid race with either characteristic black or brown spots running down the sides of their neck or an odd forehead. The forehead type were only seen in one episode of Star Trek: The Next Generation. The spotted Trills appeared throughout Deep Space Nine.

The symbionts are helpless, worm-shaped lifeforms who contain the memories of their previous hosts, and who inhabit the abdomens of the humanoid hosts. When a host and a symbiont are joined, the resulting individual is considered a new being.The Trill society is a complex and elitist one. Only joined Trills can be politicians and they take all the planet's decisions. When a host dies, the symbiont is transplanted into a new host. A symbiont who is neither implanted into a new host nor returned to their habitat (pools of nutrient-rich liquid on the Trill homeworld) will quickly die, as will a joined Trill host from whom the symbiont is removed after the first or second day.

It was originally assumed that only a small fraction of the Trill population was capable of being joined, a myth which the Trill government continues to perpetuate. This is because the joining of the Dax symbiont with the host Joran (Curzon's predecessor), was a disaster - Joran was insane and a murderer. Joran's joining with Dax was covered up and all records of it were erased. The Trill government attempted to blame the failure on Joran's unsuitability as a host, but the truth was that Joran had passed the host screening tests and was technically a stable host - as was nearly half of the Trill population. The government dares not let this information become public, lest the symbionts become a commodity to be bought, sold and fought over by the public - as long as it is widely believed that only a small fraction can become hosts, the government reasons, then such widespread hysteria can be avoided.

In rare cases, Trill symbionts can be joined with non-Trill humanoids, but the differences in biology means the results are often unstable. ("The Host", TNG). Commander William Riker was briefly joined to the Odan symbiont so that Odan could complete peace negotiations, and to keep Odan alive until a new Trill host could arrive. While this effort saved Odan's life, it nearly caused Riker's death.

A joined Trill is known by the given name of the host followed by the name of the symbiont; for example, when Ezri Tigan was joined with the symbiont Dax, her name became Ezri Dax.

Trill society has a taboo against resuming relationships with loved ones from one's past joining, on the principle that each life must be unique. ("Rejoined", DS9)

Notable Trills

• Dax
  • Curzon Dax
  • Jadzia Dax
  • Ezri Dax
• Lenara Kahn

External links

• Trill at Memory Alpha, a Star Trek WikiWiki.