Many English words start with vowels, for instance, “I,” “eye,” “ate,” “at,” “air,” and many more. Many times, in English, we might put a glottal stop (ʔ) before the vowel. So when we say “Air is useful,” we are making the sounds [ʔɛr ɪz usfl̩], There is a catch in our throat just before the ‘a’ [ɛ]. However, we do this more often in slow speech.
- Black or white [blæk ʔor wit]
Would usually be said,
- Black er white [blæk ɚ wit]
So the vowel sound becomes neutral and the ‘r’ gets assimilarted. This is discussed in … XXX
How a word is said in isolation and how it is said in continuous speech will often not be the same.