The nasal vowels

Few features identify Portuguese as quickly as its nasal vowels — the sound of lã “wool”, fim “end” or bom “good”, produced with air escaping through the mouth and the nose at the same time. Alongside its seven oral vowels, the language has a parallel system of five nasal vowels, /ɐ̃ ẽ ĩ õ ũ/, which lies behind pairs such as lã [lɐ̃] and lá [la] “there”. Among the major Romance languages, only French preserves a comparably developed set of nasals.

The five nasal vowels

A vowel is nasal when, as it is produced, the velum (the soft part of the roof of the mouth) lowers and lets air resonate in the nasal cavity as well. Portuguese has five nasal timbres, spread across the same articulatory space as the oral vowels but fewer in number.

Symbol	Description	Examples
[ɐ̃]	central	*lã*, *campo*, *canto*
[ẽ]	close-mid front	*pente*, *tempo*, *lenço*
[ĩ]	close front	*fim*, *sim*, *tinta*
[õ]	close-mid back	*bom*, *ponte*, *conta*
[ũ]	close back	*um*, *mundo*, *atum*

Nasality is no mere ornament of pronunciation: it is distinctive, that is, it changes the meaning of words. That is why manto “cloak” is not mato “thicket”, nor minto “I lie” the same as mito “myth”.

Five nasals, seven orals

The nasal system is poorer than the oral one, and the asymmetry is telling. In a stressed syllable, the oral vowels distinguish two degrees of openness in the mid range — the close timbre of avô [ɐˈvo] “grandfather” against the open timbre of avó [ɐˈvɔ] “grandmother” — but that opposition vanishes under nasality. Portuguese has no open [ɛ̃] and no open [ɔ̃]: the mid nasals are always close, [ẽ] and [õ]. Likewise, the low nasal vowel is not the open [a] of pá but the higher central vowel [ɐ̃]. Nasalisation, in other words, neutralises timbre contrasts that the oral vowels keep — which is why seven orals answer to only five nasals.

How nasality is written

Portuguese spelling marks nasality in two ways, never with a «special» vowel letter:

• with the tilde (~) over the vowel — ã and õ — chiefly in the diphthongs -ão, -ãe and -õe and in words such as lã, irmã “sister”, maçã “apple”. The tilde is not a stress mark: it began in medieval writing as a small n placed above the vowel, an abbreviation that settled into a sign of nasality;
• with a nasal consonant — m or n — at the end of the syllable. One writes m before p and b and word-finally (campo, tempo, bom, um) and n before other consonants (canto, ponte, mundo, lenço, tinta).

In these cases the m or n does not stand for a full consonant: its job is to mark that the preceding vowel is nasal. Campo “field” is not [ˈkampu], with a crisp [m], but [ˈkɐ̃pu] , with the nasality lodged in the vowel itself.

Where they come from: a lost nasal consonant

The nasal vowels of Portuguese are the inheritance of a Latin nasal consonant that dissolved into the neighbouring vowel. There are two main paths. Where Latin had an -m or -n closing a syllable, the consonant gradually faded, leaving its mark on the vowel: CAMPUM > campo, TEMPUS > tempo. And where there was an intervocalic /n/, that consonant dropped entirely, surviving only as nasality — the very change that set Galician-Portuguese apart early on.

The process did not always hold: in LŪNA > lũa > lua “moon” the vowel eventually de-nasalised between vowels, whereas word-finally the nasality survived. That is why many Portuguese plurals and derivatives still keep the memory of that old n — cão ~ cães “dog(s)”, leão ~ leões “lion(s)” — in alternations that are living fossils of the language’s phonetic history.

Phonemes or sequences?

Phonologists disagree about the status of these vowels. The traditional analysis counts them as five nasal phonemes in their own right, beside the orals. A more recent analysis, argued by Mateus and d’Andrade, prefers to see them as the realisation of an oral vowel followed by an underlying nasal consonant in the syllable coda — a nasal element with no fixed place of articulation, which nasalises the vowel and rarely surfaces as a full consonant.

The strongest argument for this second reading is that the nasal consonant reappears as soon as the word takes a suffix or links to the next: the nasal vowel of fim shows its /n/ again in final; that of som “sound”, in sonoro “resonant”; that of um “one”, in the feminine uma; that of bom, in bondade “goodness”. Whichever analysis one prefers, the phonetic fact stands: nasality is contrastive, and the minimal pairs above keep their opposition.

In Brazil and in Portugal

Nasality exists on both shores of the Atlantic, but it is distributed differently.

A common mistake

For the foreign ear, the temptation is to read the nasal vowel as an oral vowel followed by a clearly audible n, and to pronounce fim as [fin] or bom as [bɔn]. The result sounds instantly like an accent, because it undoes the very thing that defines the Portuguese nasal vowel: the nasality lives in the vowel itself, not in a consonant that follows it. The trick is to lower the velum from the start of the vowel and not to close the passage with the tongue at the end — to let the nasality dissolve into the air rather than round it off with an [n] or an [m].

Why they matter

The five nasal vowels are one of the sonic signatures of Portuguese and one of the first hurdles for learners used to languages in which a nasal vowel does not distinguish words. They are also phonetically longer and slightly closer than their oral counterparts, details that reinforce their presence. They also combine with the semivowels to form the nasal diphthongs — pão [pɐ̃w̃] “bread”, mãe [mɐ̃j̃] “mother”, põe [põj̃] “puts” — which multiply nasality at the ends of words and give the language much of its music. Mastering the opposition between oral and nasal vowels is, for all these reasons, indispensable to a correct Portuguese pronunciation.