R-colored vowel
From Freepedia
In phonetics, an r-colored vowel or rhotacized vowel is a vowel either with the tip or blade of the tongue turned up during at least part of the articulation of the vowel (a retroflex articulation) or with the tip of the tongue down and the back of the tongue bunched. Both articulations produce basically the same auditory effect, a lowering in frequency of the third formant. In English, only some rhotic accents like General American contain r-colored vowels. They are rarely attested in other languages, but do occur in Dutch and some varieties of Mandarin Chinese.
The r-colored vowels of General American are /ɝ/ (as in bird) and /ɚ/ (as in dinner).
Some singers in English use r-coloured vowels extensively, for example Celine Dion.
