Written Accentuation

Written accents — the diacritical marks — are signs placed over certain vowels to show how a word is read: where the strong syllable falls and, in some cases, what the quality (timbre) of that vowel is. Portuguese accentuation is neither decorative nor arbitrary: it follows a small set of rules that start from the position of the stressed syllable and from how the word ends.

Stress versus the written accent

Two things should be kept apart. The stress (the prosodic accent) is the greater force with which one syllable of every word is pronounced — it is always there, even when nothing is written: mesa, animal, comboio. The written accent is the mark that, when the rules require it, makes that stress visible or fixes the vowel’s quality. Most Portuguese words carry no mark at all; only what the rules treat as exceptional is accented.

The four marks

European Portuguese uses four accents, each with its own function.

Mark	Vowels	Function
Acute ´	á, é, í, ó, ú	marks the stressed syllable; on a, e, o it also signals open quality
Circumflex ^	â, ê, ô	marks the stressed syllable with close quality
Grave `	à	signals the crasis (contraction of the preposition a with the article a); it does not mark stress
Tilde ~	ã, õ	indicates nasality and may fall on a stressed or an unstressed vowel

The contrast in quality is audible and meaningful: avó [ɐˈvɔ] “grandmother” stands opposed to avô [ɐˈvo] “grandfather”. The grave accent, by contrast, has no bearing on stress: it serves the crasis alone.

The rules of accentuation

The general rule is organised by the position of the stressed syllable. Words are classed as oxytones (stress on the last syllable), paroxytones (on the second-to-last) and proparoxytones (on the third-to-last). The endings that are least expected for each class are the ones that take an accent.

Class	Stress on the…	Accented when ending in	Examples
Oxytones	last	-a(s), -e(s), -o(s), -em/-ens	sofá, café, avó, também, parabéns
Paroxytones	second-to-last	-l, -r, -x, -n, -ps, -ã(s), -ão(s), -i(s), -u(s), -um(s), -on(s), diphthong	fácil, açúcar, tórax, hífen, bíceps, órfão, júri, vírus, álbum, jóquei
Proparoxytones	third-to-last	all	lâmpada, médico, sílaba, rápido

The logic is economical: paroxytones are the dominant pattern of Portuguese, so they are accented only when they end atypically; proparoxytones, on the other hand, are rare and always conspicuous, and so every one of them takes an accent.

Stressed monosyllables ending in -a, -e, -o (with or without -s) are also accented: pá, pé, só, vês, pôs.

Hiatuses and diphthongs

A stressed i or u that forms a hiatus (alone in its syllable, possibly followed by -s) takes an acute accent: saída, país, baú, juízes. The mark disappears, however, before nh (rainha, moinho) and — by the 1990 Agreement — when the vowel comes after a diphthong in a paroxytone: feiura, baiuca.

The open diphthongs éi, éu, ói keep their accent in oxytones — herói, céu, papéis, chapéu — but the 1990 Agreement removed it in paroxytones, so today one writes ideia, assembleia, heroico, jiboia. The same Agreement dropped the circumflex in verb forms ending in -eem and in the hiatus -oo: leem, veem, deem, voo, enjoo.

Differential accents

Once numerous, the accents that distinguished homographic pairs were nearly all abolished by the 1990 Agreement. They are no longer written in pelo (formerly pêlo), para (formerly pára, from the verb parar), polo or pera. Only two obligatory cases survive — pôr (the verb) against por (the preposition), and pôde (past tense) against pode (present) — together with one optional case, fôrma (a mould) beside forma, used where clarity calls for it.

One spelling, two timbres

Mastering accentuation is, at bottom, a matter of learning to hear the word: identifying the strong syllable and the vowel’s quality, then applying the matching rule. The tilde, because it marks nasality rather than stress, follows a logic of its own, treated in tilde and nasality.