Ingvaeonic nasal spirant law

The distribution of the primary Germanic dialect groups in Europe in around AD 1:
  North Germanic
  North Sea Germanic, or Ingvaeonic
  Weser–Rhine Germanic, or Istvaeonic
  Elbe Germanic, or Irminonic
  East Germanic, or Illevionic
This article contains phonetic transcriptions in the International Phonetic Alphabet (IPA). For an introductory guide on IPA symbols, see Help:IPA. For the distinction between [ ], / / and ⟨ ⟩, see IPA § Brackets and transcription delimiters.

In historical linguistics, the Ingvaeonic nasal spirant law (also called the Anglo-Frisian or North Sea Germanic nasal spirant law) is a description of a phonological development that occurred in the Ingvaeonic dialects of the West Germanic languages. This includes Old English, Old Frisian, and Old Saxon, and to a lesser degree Old Dutch (Old Low Franconian).