in the International Phonetic Alphabet,  is used for the open front unrounded vowel,  is used for the open central unrounded vowel, and  is used for the open back unrounded vowel.
ɪnðɪ ˌɪntɚnˈæʃənəl fənˈɛɾɪk ˈælfəbˌɛt,  ɪz jˈuːzd fɚðɪ ˈoʊpən fɹˈʌnt ʌnɹˈaʊndᵻd vˈaʊəl,  ɪz jˈuːzd fɚðɪ ˈoʊpən sˈɛntɹəl ʌnɹˈaʊndᵻd vˈaʊəl, ænd ɪz jˈuːzd fɚðɪ ˈoʊpən bˈæk ʌnɹˈaʊndᵻd vˈaʊəl.