Umlaut
Pronunciation : Um"laut
Part of Speech : n.
Etymology : [G., from um about + laut sound.] (Philol.)
Definition : Defn: The euphonic modification of a root vowel sound by the influence of a, u, or especially i, in the syllable which formerly followed.
Note: It is peculiar to the Teutonic languages, and was common in Anglo-Saxon. In German the umlauted vowels resulting from a, o, u, followed by old i, are written ?, ?, ?, or ae, oe, ue; as, m?nner or maenner, men, from mann, man. Examples of forms resulting from umlaut in English are geese pl. of goose, men pl. of man, etc.
Source : Webster's Unabridged Dictionary, 1913