Betazoids broke the warp drive barrier in the 22nd Century.
Betazed joined the Federation in 2273.
Betazoids appear nearly indistinguishable from Humans except for the eyes: the iris of a Betazoid eye is entirely black.
It is possible for a Betazoid to cross-breed with other humanoid species such as Humans or Klingons. A half Betazoid retains the black iris however a child who is 1/4 Betazoid is likely to have more typical human eye colouration. A typical Betazoid pregnancy lasts 10 months.
Betazoids are natural telepaths, an ability which is usually developed during adolescence. A few individuals are born with their telepathic abilities active and they are almost always extremely talented and powerful in telepathic terms, but also unable to screen out the noise of other people's minds, so they generally suffered mental problems of varying severity depending mostly on when the problem was diagnosed. Conversely, some Betazoids are born with a very low level of psionic abilities, being barely able to sense strong emotion.
The common psionic abilities of Betazoids extended from sensing thoughts and/or emotions, over projecting thoughts and/or emotions, to manipulating the minds of others. The extent of each ability is somewhat dependant on an individuals genetic psionic strength, training, their familiarity with the subject, their general mental and physical condition and the species of the scanned individual.
Betazoids are at times able to sense the thoughts, emotions or general intention of non-corporeal beings. In the case of the Q, they are only able to get a sense of the mental prowess and presence of a particular Q.
Inter-species reproduction involving Betazoids often affected the psionic abilities of the offspring – most commonly the children of such a union develop empathic abilities as their primary psionic talent, while their telepathic abilities, though existing, were rather below average for Betazoids. Usually the telepathy of these half-breeds, without extensive training, was limited to communication with other empaths or telepaths and full telepathic contact with emotionally very close persons. All full Betazoids are unable to read the thoughts of Ferengi, Breen, Ullians, or Dopterians.
Betazoids, and people with some Betazoid background can also communicate telepathically with people who are very close to them who are not usually capable of telepathy. And in some rare cases involving a close personal bond, a Betazoid can teach a non-telepath to communicate with them using their mind.
It is also possible, with some specialized training, to unlock latent telekinetic talents in some Betazoids.
Due to their telepathy, Betazoid culture embraced honesty almost to a point considered rude by other cultures.
Betazed had a complex hereditary nobility and traditionally had children genetically bonded to a future spouse.
In the Betazoid wedding ceremony, all participants are traditionally nude, not only the bride and groom, but the guests as well.
Betazoids have a pseudo-religious, semi-matriarchal society. Ruling houses, descended from various legendary figures, make up a planetary council that speaks for all citizens; each house broadly encompasses the interests of millions of people, in rough geographic locations (and along certain familial lines). The system of representation can be complicated by the fact that Betazoids can petition along their matrilineal lines in order to be heard, in much the same way that a citizen might write a letter to a representative in a representative democracy. Each house claims its mandate from its legendary founder, an acolyte of the Betazed mythic hero Krystaros.
Fortunately for them, the Betazoid telepathy and empathy meant that warfare was a largely foreign concept for much of Betazed history. The earliest records of conflict in Betazoid history indicate a spiritual war with non-corporeal entities—described as demons in ancient religious texts. Betazoids presumably evolved their telepathic abilities to combat such beings, and in the process created a society whereby honesty and compassion were paramount: Few Betazoids could bear to feel the pain or discomfort of fellow citizens, especially on a large scale.
Betazed wholeheartedly contributes to and partakes in Federation science and technology projects, and this shows. Their cities are built with large mushroom-shaped structures that rise up on thin spires, leaving more of the ground open for natural growth. Betazed contributes its telepathic expertise, psychological experience and philosophical developments to Federation civilization, and in return the Federation's strongly technical members help with advanced replication technology, engineering, and land reclamation. The result is that the average Betazoid has a very high and enjoyable standard of living, while the citizenry have little fear of discontent; an unhappy Betazoid is often quickly discovered and counseled by friends, neighbors, and family, all of whom want to re-establish the pleasant environs.