Fronting (sound change)

In phonology, fronting is a sound change in which a vowel or consonant becomes fronted, advanced or pronounced farther to the front of the vocal tract than some reference point. The opposite situation, in which a sound becomes pronounced farther to the back of the vocal tract, is called backing or retraction. Fronting may be triggered by a nearby sound, in which case it is a form of assimilation, or may occur on its own.

Assimilation
In i-mutation and Germanic umlaut, a back vowel is fronted under the influence of or  in a following syllable. This is assimilation.

Vowel shifts
In the Attic and Ionic dialects of Ancient Greek, Proto-Greek close back were fronted to. This change occurred in all cases and was not triggered by a nearby front consonant or vowel. Similarly in French and Occitan, this sound change also occurred.

In Old English and Old Frisian, the back vowels were fronted to  in certain cases. For more information, see First a-fronting and Second a-fronting.

In many dialects of English, the vowel is fronted to  or, a sound change that is sometimes called -fronting. The same sound change occurred in many dialects of Norwegian and Standard Swedish but not in Danish.

Fronting can also take place as part of a chain shift. For example, in the Northern Cities Shift, the raising of left room in the low-front area of the vowel space for  to expand. Thus, words like cot and father are often pronounced with a low-front vowel.