High back vowels

The high back vowels, /u/ and /ʊ/, behave very similarly to their front counterparts, /i/ and /ɪ/. The vowel /u/ is slightly diphthongal (hence the symbol /uw/ in some books). While /u/ is centralized in the southeastern USA (e.g. school, good), /ʊ/ may undergo ‘tensing’ and be realized as [u] before a palato-alveolar fricative coda, as in bush [buʃ], which rhymes with douche. As mentioned earlier, the distinction between /u/ and /ʊ/ is lost before a tautosyllabic /ɹ̣/ (e.g. tour) or /l/ (e.g. pull– pool); a similar situation may be observed in some other words spelled with oo (e.g. hoof, roof, root), where either vowel is acceptable. Finally, in unstressed syllables preceding another vowel, /u/ may become lax [ʊ] (e.g. gradual [gɹ̣æʤʊəl]).