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.
In many dialects of English, the vowel /u:/ is fronted to [u?:] or [?:], a sound change that is sometimes called goose-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 /æ/ 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 [æ].