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 at 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).

While all mons seem to speak the same Monese "language", dialects and (sub?)languages are known to 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.
• Dragon mons have a Draconic dialect based on Skyrim as well.
• Some Pokémon also speak in Al Bhed from Final Fantasy.