Dybo's law

Dybo's law, or Dybo–Illich-Svitych's law, is a Common Slavic accent law named after Soviet accentologists Vladimir Dybo and Vladislav Illich-Svitych. It was posited to explain the occurrence of nouns and verbs in Slavic languages which are invariantly accented on the inflectional ending. The latter is seen as an innovation from the original Proto-Balto-Slavic accent system, in which nouns and verbs either had invariable accent on the root, or "mobile" accent which could alternate between root and ending in the inflectional paradigm.