Greek has a system of five vowels /i, u, e, o, a/. The first two have qualities approaching their respective cardinal vowels[i, u], the mid vowels /e, o/ are true-mid[e̞, o̞] and the open /a/ is near-open central [ɐ]
There is no phonemic length distinction, but vowels in stressed syllables are pronounced somewhat longer [iˑ, uˑ, eˑ, oˑ, aˑ] than in unstressed syllables. Furthermore, vowels in stressed syllables are more peripheral, but the difference is not large. In casual speech, unstressed /i/ and /u/ in the vicinity of voiceless consonants may become devoiced or even elided.