Eifel rule
The Eifel rule (German: Eifeler Regel German pronunciation: [ˈaɪfəlɐ ˈʁeːɡl̩], Luxembourgish: Eifeler [ˈɑɪ̯fəlɐ] or Äifler Reegel [ˈæːɪ̯flɐ ˈʀeːʑəl]) is a phonological phenomenon consisting in the deletion of morpheme-final [n] in certain contexts, originally documented in the dialects of the Eifel region in the far west of Germany during the late 19th century. This is a sandhi phenomenon and may or may not be reflected in spelling, depending on the language concerned.