Unown is a flat, thin Pokémon shaped like an eye with appendages that make it resemble a letter or a punctuation mark. It is entirely black, except for its white sclerae. All 26 alphabetic forms of Unown have fully open eyes, while the two punctuation forms have half-closed eyes. Though each of its forms has a counterpart in the Latin alphabet, Unown is said to resemble ancient writing and hieroglyphs called Unown symbols. It is a mystery whether Unown predates or postdates written language, and therefore which one is based on the other. Unown can move its appendages independently like tentacles or fingers.

In the Japanese version of Pokémon Crystal, a researcher implies that the Unown began appearing at the Ruins of Alph after the Pokémon Communication Center was built in Goldenrod City, implying the Unown have some connection to radio waves or telecommunications. This text was translated and left unused in the English release.

The and 's research disagree on whether Unown communicates using electromagnetic waves or telepathy. Either way, it can be detected by the Pokégear radio, which interprets it as the melody of the Azure Flute. Unown has an unknown connection to . It is said that an "odd power" emerges when more than one Unown come together. Certain Unown loose in the Hisui region were capable of repelling Poké Balls that contained Pokémon, preventing them from being battled. Professor Laventon's research observed that Unown resemble human writing from other lands, though no one took him seriously. In the Pokémon movie Spell of the Unown: Entei (M03), Unown is shown to be capable of reading the thoughts of other life forms. Great numbers of Unown are capable of distorting reality to suit the dreams and wishes of whoever is in control of the Unown. However, they can only do this when more Unown are present, so it could be a shared effort rather than an ability unique to each Unown.

Unown is an extremely rare Pokémon that lives in its own dimension and rarely ventures outside. When it moves to the Pokémon world, Unown tends to stick to walls like engravings of ancient texts, or orbit other Unown, usually in ruins.

In Pokémon Crystal, the Unown are said to share a cooperative bond with .

Forms
Unown has 28 separate forms, all referred to as "One form". Pokédex 3D Pro, the Pokémon Trading Card Game, and other supplemental materials such as official guidebooks refer to each form by the letter or symbol they represent. In Generation II, there were 26 Unown forms based on Latin alphabet characters. In Generation III, two new forms were introduced as well: ? (question mark) and ! (exclamation point).

(Source: Bulbapedia)