From Bulbapedia, the community-driven Pokémon encyclopedia.
A completed Unown Dex, in alphabetical order.
The Unown Dex is a Pokédex upgrade present in Generation II. It is designed to display all 26 different types of Unown and the word that is associated with each form. The Unown Dex does not list the Unown in any specific order; rather, it lists them in the order in which the player captures them. After catching all 26 types, however, the forms will be reorganized alphabetically. Upon the player's capture of at least three different Unown and exiting the Ruins of Alph, a scientist will upgrade the player's Pokédex to support this mode. Ultimately, completing the Unown Dex also allows a player with a Game Boy Printer to print out the Unown sprites and text.
The Unown Dex is replaced in HeartGold and SoulSilver with a key item called Unown Report.
Unown Dex entries
Below, the different Unown forms are listed in alphabetical order, along with the word that they represent, as well as the Pokémon Power that they have in the Neo Series and the Poké-Power (or Poké-Body, in some cases) that they have in the Diamond & Pearl Series of the TCG.