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Grypsera (Polish pronunciation: [ɡrɨˈpsɛra]; from Low German Gripps meaning "intelligence", "cleverness") is a distinct nonstandard dialect of the Polish language, used traditionally by recidivist prison inmates. It evolved in the 19th century in the areas of the Russian partition.
The basic substrate of the dialect is Polish, but with many notable influences (mostly lexical) from other languages used in Polish lands at that time, most notably Yiddish, German, Ukrainian and Russian. It was also heavily influenced by various regional dialects of the Polish language, most notably the Bałak jargon of Lwów and the Warsaw dialect.
Initially it served the role of a cant, or "secret language", but in the late 19th century it became a standard sociolect of criminals. Grypsera is constantly evolving to maintain the status of a language understood only by a select group of inmates and not by the wardens or informers. Because of this it is currently one of the lexically richest dialects of the Polish language. Also, it is not possible to prepare a comprehensive dictionary of the dialect since it differs from prison to prison.
Phonetically, Grypsera is similar to the Warsaw dialect and shares its most notable features of assimilation of ⟨i⟩ [i] into ⟨y⟩ [ɨ] and the disappearance of nasal vowels, especially in word-final syllables.