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 in some dialects of West Germanic, which is attested in Old English, Old Frisian, and Old Saxon. By this sound change, in the combination vowel + nasal + fricative, the nasal disappeared, with compensatory lengthening of the vowel. ("Spirant" is an older term for "fricative".) The sequences in question are original -ns-, -mf-, and -nþ-.