So far the Negation group has dealt with syntactic negation — adding a word like não, nunca, or nem to a sentence. There is, however, a parallel system that operates at the word level: a small inventory of negative prefixes that turn a positive word into its negative counterpart without touching the rest of the sentence. Possível becomes impossível; fazer becomes desfazer; moral becomes amoral; democrático becomes antidemocrático. This is morphological negation, and it complements the syntactic system in important ways.
This page catalogues the productive negative prefixes of European Portuguese: the Latinate in- / im- / i- / ir- family, the highly productive native des-, the scientific a- / an-, the oppositional anti- and contra-, the explicit não-, and the partially-negative semi-. For each prefix we give the meaning, the allomorphic rules, the productivity, and the AO90 hyphenation conventions. (For prefixes outside the negative family — re-, sobre-, sub-, auto-, etc. — see the dedicated Common Prefixes page.)
Syntactic vs morphological negation
It pays to start with the contrast.
| Type | Example | What is negated |
|---|---|---|
| Syntactic | Não é possível. | The whole proposition |
| Morphological | É impossível. | The lexical meaning of possível |
These are not always interchangeable. Não é feliz and é infeliz both mean "(s/he) is unhappy," but the morphological version asserts unhappiness as a positive property; the syntactic version simply denies happiness. In careful writing the choice matters.
Não estou contente com o resultado.
I'm not happy with the result. (denies happiness)
Estou descontente com o resultado.
I'm dissatisfied with the result. (asserts dissatisfaction)
Morphological negation is often stronger and more committal. Syntactic negation is more neutral.
The in- / im- / i- / ir- family
The Latinate prefix in- is alive and well in Portuguese, but its surface form changes depending on the first sound of the stem it attaches to. This is allomorphy: a single underlying prefix with predictable surface variants.
The four allomorphs
| Form | Before | Examples |
|---|---|---|
| in- | vowels and most consonants | incapaz, inútil, incompleto, inativo, incrível, indeciso, incomum |
| im- | b, p (and m) | imperfeito, impróprio, imparcial, impensável, impossível, imóvel, imaturo |
| i- | l | ilegal, ilegítimo, ilógico, ilegível, iletrado |
| ir- (with written rr) | r | irregular, irresponsável, irreal, irrelevante, irreverente |
The rule is phonological: the n of in- assimilates to the place of articulation of the following consonant. Before the bilabials b, p, m, n becomes m. Before the liquids l, r, n drops entirely and the liquid sometimes doubles in spelling (irregular, with double r, written irr-). Before everything else, in- is preserved.
Tens uma capacidade incrível para resolver problemas.
You have an incredible capacity for solving problems.
É impossível chegar a tempo com este trânsito.
It's impossible to arrive on time with this traffic.
Estacionar aqui é ilegal depois das oito.
Parking here is illegal after eight.
O comportamento dele foi completamente irresponsável.
His behaviour was completely irresponsible.
Common Latinate pairs
The in- family forms a closed set of established adjective pairs. You can recognise a few hundred of them; you cannot freely coin new ones (you can't say insabido for "unknown" — the established negative is desconhecido).
| Positive | Negative | Translation |
|---|---|---|
| capaz | incapaz | capable / incapable |
| útil | inútil | useful / useless |
| completo | incompleto | complete / incomplete |
| certo | incerto | certain / uncertain |
| justo | injusto | fair / unfair |
| feliz | infeliz | happy / unhappy |
| perfeito | imperfeito | perfect / imperfect |
| próprio | impróprio | appropriate / inappropriate |
| parcial | imparcial | partial / impartial |
| possível | impossível | possible / impossible |
| maduro | imaturo | mature / immature |
| moral | imoral | moral / immoral |
| legal | ilegal | legal / illegal |
| lógico | ilógico | logical / illogical |
| regular | irregular | regular / irregular |
| responsável | irresponsável | responsible / irresponsible |
| real | irreal | real / unreal |
| relevante | irrelevante | relevant / irrelevant |
Ela é uma jornalista imparcial e respeitada.
She is an impartial and respected journalist.
Os argumentos dele são completamente irrelevantes para a discussão.
His arguments are completely irrelevant to the discussion.
Des-
By far the most productive negative prefix in modern PT-PT. Where in- is lexically frozen, des- can be added to almost any verb (to mean "undo X") and to many adjectives and nouns (to mean "not X" or "the opposite of X").
The three senses of des-
1. Reversal of an action. Added to verbs, des- names the inverse process — the action that undoes the original.
Acabei de fazer a cama, e o miúdo já a desfez.
I just made the bed, and the kid already undid it.
Vou desligar a televisão, está demasiado alta.
I'm going to turn off the television, it's too loud.
Tens de desatar este nó com cuidado.
You have to untie this knot carefully.
Desmontámos a estante para a transportarmos no carro.
We took the shelf apart to fit it in the car.
2. Negation of a state. Added to adjectives, des- yields the negative state.
O patrão está descontente com o relatório.
The boss is dissatisfied with the report.
É um ator relativamente desconhecido em Portugal.
He's a relatively unknown actor in Portugal.
A distribuição de rendimento é profundamente desigual.
The income distribution is profoundly unequal.
Ele é desonesto e ninguém confia nele.
He's dishonest and nobody trusts him.
3. Removal or absence. Added to nouns, des- names the absence or removal of what the noun denotes.
O desemprego juvenil continua a ser um problema sério.
Youth unemployment continues to be a serious problem.
A desesperança espalhou-se por toda a aldeia depois da cheia.
Hopelessness spread through the whole village after the flood.
A falta de água está a causar uma desidratação rápida.
The lack of water is causing rapid dehydration.
Productivity
Unlike in-, des- is freely productive. You can coin new words confidently — if there is a verb X-ar, there is, in principle, a verb desX-ar meaning "undo X-ar." Speakers do this constantly. Desconvidar (to uninvite), desinscrever (to unsubscribe), desinstalar (to uninstall) all behave this way.
Vou ter de desconvidar metade dos amigos — a sala não chega para todos.
I'm going to have to uninvite half my friends — the room isn't big enough.
Já desinstalei a aplicação, mas ainda recebo as notificações.
I've already uninstalled the app, but I still get the notifications.
Spelling note: des- never hyphenates
A small but important rule: des- attaches solid to its stem, even when the stem begins with h. The h does not block the prefix.
desumano (not des-humano)
inhuman
desonesto (not des-honesto)
dishonest
desidratado (not des-hidratado)
dehydrated
This is one of the few exceptions to the general AO90 rule about hyphenation before h.
A- / An- — privative, scientific
Borrowed from Greek (and reinforced by Latin), a- (and its variant an- before vowels) is the prefix of absence. It carries a more technical, scientific, or learned tone than in- or des-. Using a- on an everyday adjective sounds odd; it lives in medical, philosophical, and scientific vocabulary.
Forms
| Form | Before | Examples |
|---|---|---|
| a- | consonants | amoral, apolítico, assexuado, ateu, atemporal |
| an- | vowels (avoiding hiatus) | anaeróbio, anarquia, anestesia, anomalia, analfabeto |
Ele declara-se apolítico, mas tem opiniões fortes sobre tudo.
He declares himself apolitical, but has strong opinions on everything.
A bactéria é anaeróbia — sobrevive sem oxigénio.
The bacterium is anaerobic — it survives without oxygen.
O texto descreve uma personagem amoral, indiferente ao bem e ao mal.
The text describes an amoral character, indifferent to good and evil.
Em Portugal, a taxa de analfabetismo caiu drasticamente desde os anos setenta.
In Portugal, the illiteracy rate has fallen dramatically since the seventies.
A- vs in-: a critical distinction
A- means "without, lacking" — the absence of a property. In- means "not" — the negation of a property. The contrast comes alive in amoral vs imoral:
- Amoral: outside the moral domain altogether; a-moral.
- Imoral: positively immoral; against morals.
Os animais são amorais — não pensam em termos de certo ou errado.
Animals are amoral — they don't think in terms of right or wrong.
As ações dele foram imorais e devem ser denunciadas.
His actions were immoral and must be denounced.
The same contrast operates in atípico (atypical, outside the typical pattern) vs intolerável (intolerable, against tolerance). The shades matter in academic and journalistic registers.
Anti- — opposition, against
A modern productive prefix meaning "against, opposing." It attaches to nouns and adjectives.
Tomei um antibiótico durante uma semana.
I took an antibiotic for a week.
O acórdão foi declarado anticonstitucional pelo Tribunal.
The ruling was declared unconstitutional by the Court.
Os manifestantes antifascistas encheram a Praça do Comércio.
The antifascist protesters filled Praça do Comércio.
Não consigo ver um filme de super-heróis sem pensar no típico anti-herói da nossa geração.
I can't watch a superhero film without thinking about the typical anti-hero of our generation.
AO90 hyphenation rule for anti-
Under the Acordo Ortográfico 1990, anti- is written:
- with a hyphen when the stem begins with h (because of h) or i (because the prefix-final i meets a stem-initial i).
- solid, with double consonant when needed, otherwise. Before r and s, the consonant is doubled in writing.
| Stem begins with | Rule | Examples |
|---|---|---|
| h | hyphen | anti-herói, anti-histamínico, anti-humano |
| i | hyphen | anti-inflamatório, anti-imperialista |
| r | solid, double r | antirracista, antirreligioso, antirrugas |
| s | solid, double s | antissemita, antissocial, antisséptico |
| other | solid | antibiótico, antidemocrático, antifascista, antidepressivo, anticorpo |
Comprei um anti-inflamatório na farmácia.
I bought an anti-inflammatory at the pharmacy.
O movimento antirracista organiza uma marcha amanhã.
The antiracist movement is organising a march tomorrow.
A campanha antitabaco teve um impacto enorme nos jovens.
The anti-smoking campaign had an enormous impact on young people.
Contra- — against, counter
Less productive than anti- but still active in modern PT-PT, with a slightly different flavour: where anti- often expresses ideological opposition, contra- is more about direct opposition or counterforce.
O contra-ataque chegou tarde e custou-nos o jogo.
The counter-attack came late and cost us the game.
Leia atentamente as contraindicações do medicamento.
Read the medication's contraindications carefully.
Estás a contradizer-te. Há uma hora disseste exatamente o oposto.
You're contradicting yourself. An hour ago you said exactly the opposite.
Esta dieta acabou por ser contraproducente — ganhei peso em vez de perder.
This diet ended up being counterproductive — I gained weight instead of losing.
AO90 rule for contra-
Hyphen when the stem begins with a (the prefix-final a meets a stem-initial a) or h. Otherwise solid; before s the consonant doubles.
| Stem begins with | Rule | Examples |
|---|---|---|
| a | hyphen | contra-ataque, contra-almirante |
| h | hyphen | contra-harmónico (rare) |
| s | solid, double s | contrassenha, contrassinalado |
| other | solid | contradizer, contraproducente, contraindicação, contraponto |
Não- — explicit, transparent negation
The literal "non-." Used when no Latinate or native prefix exists for the concept being negated, or when transparency is preferred over suggesting an intermediate state. Always written with a hyphen.
Os não-fumadores podem entrar pela porta lateral.
Non-smokers can enter through the side door.
A não-violência foi o princípio central do movimento de Gandhi.
Non-violence was the central principle of Gandhi's movement.
O contrato sanciona a não-conformidade com as regras.
The contract penalises non-compliance with the rules.
A não-resposta também é uma forma de resposta.
Non-response is also a form of response.
Não- is especially common in legal, administrative, and academic registers, where precision matters and the writer wants to avoid the sometimes-ambiguous overtones of des- or in-.
Semi- — half, partly
Strictly speaking semi- expresses partiality rather than negation, but it lives in the same morphological neighbourhood and often carries a slightly negative connotation ("only half X, not fully X").
AO90 rule for semi-
Hyphen before h or before another i. Solid otherwise.
| Stem begins with | Rule | Examples |
|---|---|---|
| h | hyphen | semi-histórico, semi-humano |
| i | hyphen | semi-intensivo, semi-iletrado |
| other | solid | semifinal, semicírculo, semianalfabeto, semiprivado |
A nossa equipa chegou à semifinal pela primeira vez em dez anos.
Our team reached the semifinal for the first time in ten years.
A escola oferece um regime semi-intensivo para alunos trabalhadores.
The school offers a semi-intensive programme for working students.
Vivemos numa zona semirrural, a meia hora de Lisboa.
We live in a semi-rural area, half an hour from Lisbon.
Productivity summary
Not all negative prefixes are equally available to coin new words. From most to least productive in modern PT-PT:
| Prefix | Productivity | Notes |
|---|---|---|
| des- | HIGHLY productive | Freely formed on verbs; widely on adjectives and nouns |
| não- | Highly productive | Especially in formal/legal contexts |
| anti- | Productive | Modern coinages: antivacinas, antitabaco |
| contra- | Productive | Particularly in technical and political vocabulary |
| in-/im-/i-/ir- | Lexically frozen | Hundreds of established pairs; new coinages rare |
| a-/an- | Productive in scientific/technical | Rare in everyday language |
| semi- | Productive | "Half-X" sense common in modern coinages |
AO90 hyphenation rules — the gist
The Acordo Ortográfico 1990 unified PT-PT and PT-BR spelling and rationalised hyphen use. For negative prefixes, the recurrent rules are:
- Hyphen before h, except for des- and re- which always fuse solid (desumano, reabilitar).
- Hyphen when the prefix-final letter equals the stem-initial letter (vowel + same vowel): anti-imperialista, contra-ataque, micro-organismo.
- Solid (no hyphen) otherwise, with consonant doubling where needed: antirracista (double r), antissemita (double s), contrassenha (double s).
- Always-hyphenated prefixes (regardless of stem): ex-, pós-, pré-, pró-, sem-, recém-, vice-. Não- belongs to this set in practice.
anti-herói (h → hyphen), antibiótico (b → solid), antirracista (r → solid + rr), anti-inflamatório (i + i → hyphen)
Sample contrasts for the *anti-* hyphen rule
contra-ataque (a + a → hyphen), contradizer (d → solid), contrassenha (s → solid + ss)
Sample contrasts for the *contra-* hyphen rule
semifinal (f → solid), semi-histórico (h → hyphen), semi-intensivo (i + i → hyphen)
Sample contrasts for the *semi-* hyphen rule
Common mistakes
❌ inprovável
Wrong allomorph — before *p*, *in-* becomes *im-*.
✅ improvável
improbable
❌ inlegal
Wrong allomorph — before *l*, *in-* drops the *n*.
✅ ilegal
illegal
❌ desir, desfeliz
*Des-* doesn't attach freely to all stems. *Unhappy* is *infeliz*; *to leave* is *partir*. Don't coin where the language already has a word.
✅ infeliz, partir
unhappy, to leave
❌ des-honesto, des-humano
*Des-* never takes a hyphen, even before *h*. It is one of the few exceptions to the *h*-hyphen rule.
✅ desonesto, desumano
dishonest, inhuman
❌ semi-circular, semi-final
Under AO90, *semi-* fuses solid before consonants. Hyphen only before *h* or *i*.
✅ semicircular, semifinal
semicircular, semifinal
❌ antiherói, antiinflamatório, antiracista
Hyphen before *h* and *i*; before *r* the *r* doubles in writing without a hyphen.
✅ anti-herói, anti-inflamatório, antirracista
anti-hero, anti-inflammatory, antiracist
❌ contraataque, contraindicação with hyphen as 'contra-indicação'
*Contra-* hyphenates only before *a* and *h*. Before *i* it is solid: *contraindicação*.
✅ contra-ataque, contraindicação
counter-attack, contraindication
❌ naofumador, não fumador (separated)
*Não-* is one of the always-hyphenated prefixes. Both 'no hyphen' and 'space' are wrong.
✅ não-fumador
non-smoker
❌ amoral when meaning 'wicked'
*Amoral* means 'outside the moral domain' (e.g. animals). For 'wicked, against morals' use *imoral*.
✅ Aquele homem é imoral, não amoral.
That man is immoral, not amoral.
Key takeaways
- Portuguese has both syntactic (sentence-level) and morphological (word-level) negation. Morphological negation is built with prefixes.
- The in- / im- / i- / ir- family is allomorphic and lexically frozen: hundreds of established pairs, but you cannot coin new ones freely.
- Des- is the most productive negative prefix; it expresses reversal (verbs), negation of state (adjectives), and removal/absence (nouns).
- A- / an- is a scientific/technical prefix from Greek; it expresses absence rather than active negation. Amoral ≠ imoral.
- Anti- is productive for opposition; contra- for direct counterforce; não- for transparent "non-" formations, especially in formal registers.
- AO90 hyphenation: hyphen before h (except des- and re-), hyphen when prefix-final and stem-initial vowels match, otherwise solid. Não-, ex-, pós-, pré-, pró- always hyphenate.
- Before r and s, prefixes ending in a vowel (like anti-, contra-, semi-) double the consonant in writing rather than hyphenating: antirracista, antissemita, contrassenha.
Related Topics
- Negation OverviewA1 — How to make sentences negative in Portuguese — from the basic não before the verb to the double-negation system, pre-verbal negatives, tag questions, and emphatic strengthenings.
- Nem (Not Even, Neither/Nor)A2 — The many uses of nem in European Portuguese — negative coordinator, not-even emphatic, idiomatic refusals, and the characteristic PT-PT hedge nem por isso.
- Common PrefixesB1 — The productive prefixes of European Portuguese — what they mean, what they attach to, and the Acordo Ortográfico 1990 rules that govern their hyphenation.
- Word Formation OverviewB1 — How Portuguese creates new words — derivation (prefixes and suffixes), composition (compound words), conversion, and the orthographic rules of the Acordo Ortográfico 1990.
- Common Spelling ErrorsA2 — The Portuguese spelling rules learners get wrong most often — ss vs ç, when to use h, silent letters, and the full system of accents (post-1990 orthography).