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 philological 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-.

Compare the first person plural pronoun us in various old Germanic languages:

• Old English ūs
• Old Frisian ūs
• Old Saxon ūs
• Old High German uns
• Middle Dutch ons
• Gothic uns

Gothic represents East Germanic, and its correspondence to German and Dutch shows it has the more original form. The /n/ has disappeared in English, Frisian and Old Saxon, with compensatory lengthening of the /u/.

Likewise:

• Germanic *tanþ- becomes English tooth (cf. Dutch tand, German Zahn).
• Germanic *anþara- becomes English other (cf. German & Dutch ander- ^*).
• Germanic *fimf becomes English five, Dutch vijf (cf. German fünf).
• Germanic *samft- becomes English soft, Dutch zacht ^* (cf. German sanft).
• Germanic *gans- becomes English goose (cf. Dutch gans, German Gans).

Note that Dutch is inconsistent, following the law in some words but not others; this must be understood in terms of the standard language drawing from a variety of dialects, only some of which were affected by the sound change. Similarly, certain North German dialects retain Old Saxon forms, with the result that a very few words in Modern Standard German have this shift: alongside sanft German also has sacht, both meaning "soft", "gentle".

One consequence of this is that English has very few words ending in -nth; those which do exist must be more recent than the productive period of the Anglo-Frisian nasal spirant law:

• month - in Old English this was monaþ (cf. German Monat); the intervening vowel made the law inoperable.
• tenth - a neologism in Middle English. Germanic *tehunþ- did originally follow the law, producing Old English tēoþa (Modern English tithe), but the force of analogy to the cardinal number ten caused Middle English to recreate the regular ordinal.
• plinth - a Greek loan-word in Modern English ().

West Germanic languages | Historical linguistics | Old English language | Sound laws

Ingveonismen | Ingvaeoonse klankverschuivingen