Andorian

The Andorians were a warp-capable humanoid species from the moon Andoria, capital of the Andorian Empire, in the Alpha Quadrant. In 2161, their homeworld became a founding member of the United Federation of Planets.

Biology

Andorians had blue skin and white to gray hair. Some individuals had fleshy protruding structures above their eyes instead of eyebrows. The Aenar subspecies had white skin and, unlike mainstream Andorians, were blind and telepathic. Hybrids between Andorians and Aenar had pale greenish skin and were not blind. (Star Trek: The Motion Picture; ENT: "United", "These Are the Voyages..."; DIS: "Despite Yourself"; LD: "Second Contact")
Andorians had a higher metabolic rate than Humans, which could theoretically permit a Human opponent to best an Andorian in hand-to-hand combat by simply exhausting them. This also made them especially vulnerable to phase-pulse infection; even minor phase-pistol injuries could prove fatal. (ENT: "United") However, they demonstrated resistance to a wide range of environmental conditions. In a climate where the temperature was near the boiling point of water, an Andorian could still thrive, despite losing ten percent of their body weight in two days. (ENT: "The Aenar")
Since Andorian physiology made intravenous injection impossible, physicians administered medication through intramuscular injection instead. (TOS: "Whom Gods Destroy")
Andorians could require a tonsillectomy. (DIS: "Choose Your Pain")
Antennae
One of the most distinctive traits of Andorians and Aenar was a pair of antennae on top of their heads. The antennae were moved by voluntary muscles and could be controlled separate from one another. (ENT: "United")
Although an antenna cut off or otherwise separated would eventually grow back, it could be humiliating to lose one or both antennae. (ENT: "United")
Blood
Andorians were true blue-bloods: Talas' blood displayed non-viscous, translucent qualities, and was as dark blue as Shran's abrasions. Andorian tongues and gums alternated from dark blue to pink. (ENT: "United")
Andorians had increased perfusion in colder environments. On breathing the freezing air of Andoria, Shran remarked how it "really gets the blood running!" (ENT: "The Aenar")

History

The Andorians originated from the icy moon of Andoria. Early in their history, the Aenar diverged from them as a subspecies, having retreated to the Northern Wastes, thenceforth considered a myth until the early 22nd century. (ENT: "The Aenar")
The Andorians employed ice-cutters to navigate their homeworld; the first to circumnavigate the moon was called Kumari, a name that was carried on to future Andorian vessels. (ENT: "United")

Mirror universe

In the mirror universe, Andorians were among multiple races conquered by the Terran Empire by 2155.
While some Andorians served aboard Starfleet vessels like the ISS Avenger that year, other Andorians took part in a rebellion against the Terran Empire. In one engagement, at least two Andorian battle cruisers were present. (ENT: "In a Mirror, Darkly, Part II")
Andorian rebels continued to resist the Empire well into the 23rd century. (DIS: "Despite Yourself", "The Wolf Inside")

Society

Andorians were a militaristic race, exemplified in small part by weaponry without stun settings. They considered it an honor to serve in their Imperial Guard, and military rank greatly influenced social reputation. Deploring dishonesty – and never fighting without reason – Andorians were nonetheless capable of duplicity. The Andorians were suspicious and volatile. They considered themselves deeply emotional, passionate, even violent; not known for their charity or sympathy, they placed a high value on family. (ENT: "The Andorian Incident", "Cease Fire", "Babel One", "United"; TOS: "Journey to Babel"; TAS: "Yesteryear")
A chirurgeon was a type of medical practitioner on Andoria. (DS9: "Prophet Motive") Culture and tradition
A crucial part of Andorian tradition was the Ushaan, a code of honor demanding a duel to the death, with combatants pitted against one another using an ushaan-tor ice miner's tool. A vast body of regulations – up to twelve thousand amendments – bound this code. Such a fight could be called off if one combatant disabled the other enough to prevent its continuance. Though Ushaan could be called by someone to avenge a personal loss, there existed a right of substitution wherein each combatant could offer up a replacement, and married combatants could postpone duels indefinitely if they had no children to continue their clans. (ENT: "United")
Members of the Andorian Imperial Guard who died far from home could count on their companions to transport a part of them, for example some of their blood, back to the Andorian ices. As a special honor, the blood of a dead person could be taken to the Wall of Heroes on Andoria. (ENT: "United")

Females enjoyed an equal position in Andorian society, and as soldiers, were as capable as males. Also, they could initiate an intimate relationship by assaulting a male. Andorian weddings required groups of four people, except under certain circumstances. (ENT: "Cease Fire", "Proving Ground", "Babel One"; TNG: "Data's Day")
While it was not specifically stated, this might be an indication of polygamy. Andorians were well known for their determination and endurance in physical combat. On Andoria, they were taught how to fight with an ushaan-tor when they were children. (VOY: "One Small Step"; ENT: "United")
Andorians made prodigious artists; Ezri Dax's mother, Yanas Tigan, bought hand-painted Andorian tiles for her solarium in 2375, and the Andorian Academy was widely considered the best art school in the Federation. (DS9: "Prodigal Daughter")
Like most species, Andorian society also harbored the idea of Heaven, a dream of a place from which creation sprang. According to Sybok, the word for it in the Andorian language was "unpronounceable." (Star Trek V: The Final Frontier)