The oral vowels

In stressed syllables, European Portuguese has a system of seven oral vowels: /i/, /e/, /ɛ/, /a/, /ɔ/, /o/ and /u/. It is one of the richest vowel inventories among the Romance languages, and the foundation on which such distinctive features of Portuguese as vowel reduction and nasality are built. Knowing these seven qualities is the first step in describing how Portuguese is pronounced.

The vowel triangle

The vowels are told apart by two main articulatory parameters: the height of the tongue (from close to open) and its backness (front, central and back vowels). Plotted along these axes, the seven vowels trace the classic vowel triangle, with /i/ and /u/ at the upper corners and /a/ at the base.

Symbol	Description	Example	Meaning
[i]	close front	*vi*	I saw
[e]	close-mid front	*vê*	(he) sees
[ɛ]	open-mid front	*pé*	foot
[a]	open central	*pá*	spade
[ɔ]	open-mid back	*pó*	dust
[o]	close-mid back	*avô*	grandfather
[u]	close back	*tu*	you

The front vowels are produced with spread lips; the back vowels with lip rounding — which is why /u/, /o/ and /ɔ/ are also called rounded vowels.

The aperture contrast

The most distinctive trait of the system is the opposition, within the mid vowels, between a close (close-mid) quality and an open (open-mid) one. The spelling does not mark it consistently — e and o can stand for either the close or the open sound — but the difference is phonological: it changes the meaning of words.

The written accent helps in part: the circumflex typically marks the close vowel (pôde ‘could’, avô) and the acute the open one (pode ‘can’, avó) — though most words carry no accent, and their vowel quality must then be learned case by case.

The central vowel [ɐ]

Alongside the open /a/ of pá, European Portuguese has a closer central vowel, [ɐ], which occurs in stressed syllables chiefly before a nasal consonant, as in cama [ˈkɐmɐ] ‘bed’ or câmara [ˈkɐmɐɾɐ] ‘chamber’. Phonologists disagree as to whether this [ɐ] is an eighth vowel or merely an allophone of /a/.

Stressed syllables only

These seven contrasts are realised in full only in the stressed syllable. In unstressed position the system shrinks dramatically: the mid and low vowels tend to close and centralise, and the final unstressed inventory is reduced to little more than [ɨ], [ɐ] and [u]. This is why the same root changes its vowel depending on whether a syllable is stressed.

This weakening of unstressed vowels — far stronger than in other varieties — is what gives European Portuguese its characteristic, seemingly «compressed» rhythm, and is treated in detail in the article on vowel reduction.

Why they matter

The seven oral vowels are the starting point of almost all of Portuguese phonology. They combine with glides to form diphthongs, they nasalise before a nasal consonant to yield the nasal vowels, and they reduce in unstressed position by rules peculiar to the European variety. Mastering the opposition between close and open qualities is, moreover, indispensable to correct pronunciation — and one of the hardest hurdles for learners of Portuguese.