Monese

Monese is the name given to the language spoken by Pokémon. It is not normally able to be understood by humans, but anyone who has used the Human-Pokémon armband can understand it, and it can be learned just like any human language.

Known methods for humans to understand Monese include:

• Being pretty much raised by Pokémon from a young age. (N and Fool).
• Using a Psychic type to translate. (Tagg before his trip to the PMD universe.)
• Via a Glitch (Wolf).
• Visiting the Dream World (Crewe).
• Being transformed into a Pokémon either through a trip to the PMD universe (Tagg) or by wearing the human to Pokémon armband (Rex).
• Being formally taught the language (Umbramatic).
• Having a Pokémon directly translate through electronic methods (Ren)

While all mons seem to speak the same Monese "language", dialects and (sub?)languages are known to exist:

• Dialects of real world languages exist.
  • Members of some Murkrow Mafias speak in "Russian Monese".
  • There also exists Chinese, Japanese, Spanish, and Italian.
• Kanto and Johto Nidoran employ Lapine from Watership Down in formal situations. (Information available at Bits'n'Bob-stones)
• Dragon mons have a Draconic dialect based on Skyrim as well. (Information available at http://thuum.org/ )
• Some Pokémon also speak in Al Bhed from Final Fantasy Ⅹ. (Information available at Al Bhed (Final Fantasy Wiki))