A Portuguese prefix (prefixo) is a bound morpheme that attaches to the front of a stem to shift its meaning. Unlike suffixes, prefixes usually do not change the word class — fazer is a verb and desfazer is still a verb; contente is an adjective and descontente is still an adjective. What the prefix changes is the sense: negation, reversal, repetition, position, intensity, or time.
This page covers the prefixes you will actually encounter and use in European Portuguese, with the orthographic rules that govern their spelling under the Acordo Ortográfico 1990 (AO90). Hyphenation is the area where learners most often go wrong; we give the rule for every prefix, note where AO90 changed the pre-2009 spelling, and flag the handful of cases where two spellings are still tolerated.
The major prefix families
Portuguese prefixes cluster into semantic families. Learning them by family, rather than alphabetically, gives you a meaning-network rather than a list.
| Family | Prefixes | Sense |
|---|---|---|
| Negation / reversal | des-, in-/im-/i-/ir-, a-, anti-, contra- | not X; the opposite of X; undo X |
| Repetition | re- | do X again |
| Position / direction | sobre-, sub-, inter-, trans-, extra-, intra- | above, under, between, across, outside, inside |
| Time | pre-/pré-, pós-, ante- | before, after |
| Self / shared | auto-, co- | by oneself; together with |
| Quantity / intensity | bi-, tri-, multi-, super-, hiper-, mega-, semi- | two, three, many, extreme, half |
| Former / current | ex-, pré- | used to be X; currently X |
Negation and reversal
des-
Far and away the most productive prefix in modern PT-PT. Its base meaning is reversal of an action (a verb) or negation of a quality (an adjective or noun). You can safely coin new words with des-: if you do something, you can usually un-do it by adding des-.
fazer → desfazer
to do → to undo
ligar → desligar
to turn on → to turn off
arrumar → desarrumar
to tidy → to untidy, make a mess of
contente → descontente
happy → unhappy
igual → desigual
equal → unequal
honesto → desonesto
honest → dishonest (note: only one *s*, not *deshonesto*)
Acabei de desligar o computador e já me arrependo.
I just turned off the computer and I already regret it.
A distribuição de recursos é profundamente desigual nesta região.
The distribution of resources is profoundly unequal in this region.
Ele é um tipo desonesto, não confies nada do que ele te disser.
He's a dishonest guy, don't trust a word of what he tells you.
Spelling rule: des- stays solid with its stem. No hyphen, even before h (desumano, not des-humano), which is one of the few exceptions to the general AO90 -h- rule.
in- / im- / i- / ir-
A classical Latin prefix that has survived into modern PT-PT as an allomorph. The form depends on the first consonant of the stem, and the allomorphy is phonetic — PT-PT assimilates the n to the following consonant exactly as Latin did.
| Form | Before | Examples |
|---|---|---|
| in- | vowels, most consonants | incapaz, inútil, indeciso, incomum |
| im- | b, p, m | imparável, impaciente, imperfeito, imóvel |
| i- | l, r | ilegal, irreal, irreversível, ilógico |
| ir- (written double r) | r (with r gemination in spelling) | irregular, irresponsável, irrelevante |
A situação é complicada mas não é irremediável.
The situation is complicated but not irremediable.
Estás a ser impaciente — dá-lhe tempo para responder.
You're being impatient — give him time to respond.
É ilegal estacionar aqui depois das sete da tarde.
It is illegal to park here after seven in the evening.
O comportamento dele é absolutamente irresponsável.
His behaviour is absolutely irresponsible.
Productivity: in-/im-/i-/ir- is productive but less freely so than des-. In practice, you add it to Latinate adjectives (capaz → incapaz, perfeito → imperfeito), not to everyday ones. Feliz stays feliz, never infeliz... actually, infeliz exists, but sabido does not become insabido. There is a lexical list of which adjectives accept in-, and you cannot coin freely.
a-
Negation in technical and scientific vocabulary. Before a consonant it is a-; before a vowel it becomes an-.
a- + normal = anormal
abnormal (medical / scientific)
a- + simétrico = assimétrico
asymmetric (note the doubled *s*)
an- + aeróbio = anaeróbio
anaerobic (without oxygen)
a- + político = apolítico
apolitical, non-political
Unlike in-, a- does not generally negate everyday adjectives. Pessoa apolítica is fine; pessoa afeliz is not. Use a- for Greek/Latin-origin terms.
anti-
"Against, opposing." Highly productive in modern PT-PT — anticovid, antifascista, antidepressivo, antirracista (or anti-racista, see below).
Tomou um antibiótico e em dois dias estava melhor.
He took an antibiotic and in two days he was better.
Os anti-histamínicos causam sonolência em algumas pessoas.
Antihistamines cause drowsiness in some people.
Ele é anticonstitucional naquilo que defende.
What he defends is unconstitutional.
Spelling rule (AO90): anti- takes a hyphen before a stem beginning with h or i. Elsewhere it is written solid.
| Stem begins with | Rule | Examples |
|---|---|---|
| h | hyphen | anti-higiénico, anti-histamínico, anti-humano |
| i | hyphen | anti-inflamatório, anti-imperialista |
| r (written double) | no hyphen, doubled r | antirracista, antirreligioso |
| s (written double) | no hyphen, doubled s | antissemita, antissocial |
| other | no hyphen | antibiótico, antidroga, antifascista, anticorpo |
Compre um bom anti-inflamatório na farmácia da esquina.
Buy a good anti-inflammatory at the pharmacy on the corner.
Os comícios antifascistas encheram a praça.
The anti-fascist rallies filled the square.
contra-
"Against, counter-." Less productive than anti- but still active. The AO90 hyphen rule: hyphen when the stem begins with a or h (because the prefix ends in a).
contra- + ataque = contra-ataque
counter-attack (two *a*'s meet, so hyphen)
contra- + indicação = contraindicação
contraindication (no hyphen, stem begins with *i*)
contra- + dizer = contradizer
to contradict (no hyphen)
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.
Repetition: re-
"Again, once more," sometimes intensification. Very productive.
re- + fazer = refazer
to redo
re- + começar = recomeçar
to restart
re- + ler = reler
to reread
re- + eleger = reeleger
to re-elect (two *e*'s, written solid under AO90)
re- + organizar = reorganizar
to reorganize
Vou ter de refazer todo o relatório, o chefe não gostou nada.
I'll have to redo the whole report, the boss didn't like it at all.
O presidente foi reeleito com uma larga maioria.
The president was re-elected with a large majority.
Spelling rule (AO90): re- takes no hyphen, even before e or h. Two e's are simply written out: reeleger, reescrever, reencontro. This is one of the clearest AO90 simplifications — pre-2009, you sometimes saw re-eleger with a hyphen; the hyphen is no longer used.
Re- can also intensify rather than repeat: rebuscado (overly elaborate), remoer (to mull over, chew on). The intensifying sense is less predictable; treat these as lexical items.
O estilo dele é rebuscado, cheio de construções complicadas.
His style is overly elaborate, full of complicated constructions.
Time: pre- / pré- and pós-
pre- (fused, no accent) vs pré- (hyphenated with accent)
A genuine source of confusion. Portuguese inherits two forms from Latin prae-: one fused into the stem without a hyphen and without a written accent (preparar, prevenir, prever), and one used productively today with a hyphen and written accent (pré-histórico, pré-aviso, pré-reforma).
| Form | Use | Examples |
|---|---|---|
| pre- (no hyphen, no accent) | Latin-origin verbs, fossilized | preparar, prevenir, prever, predizer, presumir |
| pré- (hyphen, accent) | modern coinages, temporal "before" | pré-histórico, pré-aviso, pré-candidato, pré-escolar, pré-produção |
Ele sabe prever o que os outros vão dizer antes de falarem.
He can predict what others are going to say before they speak.
A educação pré-escolar é fundamental para o desenvolvimento.
Pre-school education is fundamental for development.
O pré-aviso tem de ser entregue por escrito.
The notice must be submitted in writing.
The acute accent marks pré- as a separate word-unit, phonetically stressed; pre- in preparar is unstressed and part of a single word. Native speakers feel the difference.
pós-
"After." Always written with an accent and a hyphen.
pós- + graduação = pós-graduação
postgraduate degree (note the hyphen, always)
pós- + parto = pós-parto
postpartum
pós- + guerra = pós-guerra
postwar
A literatura do pós-guerra é marcada pelo existencialismo.
Postwar literature is marked by existentialism.
ante-
Also "before." Mostly solid, no hyphen, except before h or i.
ante- + ontem = anteontem
the day before yesterday
ante- + braço = antebraço
forearm
ante- + sala = antessala
anteroom (double *s*)
Position: sobre-, sub-, super-
sobre-
"Above, on top of, excess." Written solid, no hyphen.
sobre- + voar = sobrevoar
to fly over
sobre- + viver = sobreviver
to survive
sobre- + carga = sobrecarga
overload, excess burden
sobre- + taxa = sobretaxa
surcharge
O avião sobrevoou a cidade três vezes antes de aterrar.
The plane flew over the city three times before landing.
Foi uma sobrecarga de trabalho que ninguém conseguiu aguentar.
It was a workload overload that nobody could handle.
super-
A more modern alternative to sobre-, used in scientific and pop coinages. Takes a hyphen before h or r (AO90 rule: same letter or h).
| Stem begins with | Rule | Example |
|---|---|---|
| h | hyphen | super-homem |
| r | hyphen | super-resistente, super-rápido |
| other | no hyphen | superdotado, supermercado, superproteger |
Ele é um miúdo superdotado — já fala três línguas aos oito anos.
He's a gifted kid — he already speaks three languages at eight years old.
Comprei pilhas super-resistentes para a máquina fotográfica.
I bought super-resistant batteries for the camera.
sub-
"Under, below, insufficient." AO90: hyphen before b, h, or r.
| Stem begins with | Rule | Example |
|---|---|---|
| b | hyphen | sub-base |
| h | hyphen | sub-humano |
| r | hyphen | sub-região, sub-reptício |
| other | no hyphen | subterrâneo, submundo, subavaliar, subir |
O metro circula subterraneamente por toda a cidade.
The metro runs underground throughout the city.
Os salários nesta área estão claramente subavaliados.
Salaries in this area are clearly underrated.
As sub-regiões do Alentejo têm características muito distintas.
The sub-regions of Alentejo have very distinct characteristics.
Self and shared: auto- and co-
auto-
"Self." The AO90 rules for auto- are among the most changed; many pre-2009 auto- compounds lost their hyphen.
| Stem begins with | AO90 rule | Example |
|---|---|---|
| o (same vowel as prefix) | hyphen | auto-observação, auto-organização |
| h | hyphen | auto-hipnose, auto-heterónimo |
| other vowel | no hyphen | autoestrada, autoajuda, autoaprendizagem |
| consonant | no hyphen | autobiografia, autocarro, autorretrato |
A autoestrada A1 liga Lisboa ao Porto.
The A1 motorway connects Lisbon to Porto.
Este livro é de autoajuda, não é academicamente sério.
This is a self-help book, not academically serious.
A auto-hipnose é uma técnica de relaxamento.
Self-hypnosis is a relaxation technique.
Note: autoestrada (one word) is the AO90 spelling; the pre-2009 spelling was auto-estrada. Both are still visible in older texts, but the modern spelling is solid.
co-
"Together with." The AO90 rule here broke decisively with tradition: most co- compounds lost their hyphen, even when the stem begins with a vowel.
co- + autor = coautor
co-author (AO90; pre-2009 was *co-autor*)
co- + existir = coexistir
to coexist
co- + operar = cooperar
to cooperate (two *o*'s written out, no hyphen)
co- + habitar = coabitar
to cohabit
co- + herdeiro = coerdeiro (AO90) or co-herdeiro (tolerated)
co-heir — AO90 drops the *h*, but the hyphenated form persists in some legal texts
Os dois autores coescreveram este ensaio durante dois anos.
The two authors co-wrote this essay over two years.
A família prefere coabitar em vez de se separar.
The family prefers to cohabit rather than separate.
Co- is an AO90 exception to the general rule about vowel sameness: pre-2009 you used a hyphen (co-operar, co-autor); AO90 writes them solid (cooperar, coautor). This is worth flagging in texts — if you see co-autor in a modern PT-PT text, it is pre-AO90 spelling and would be updated in a contemporary edition.
ex- — former
Always written with a hyphen, whatever the stem.
ex- + namorado = ex-namorado
ex-boyfriend
ex- + presidente = ex-presidente
former president
ex- + marido = ex-marido
ex-husband
O ex-presidente vai publicar as suas memórias no próximo ano.
The former president will publish his memoirs next year.
Encontrei a minha ex-namorada no supermercado — foi estranho.
I ran into my ex-girlfriend at the supermarket — it was awkward.
Quantity and intensity
bi-, tri-, multi-, poli-
Numeric prefixes from Latin (bi-, tri-, multi-) and Greek (poli-). Solid, no hyphen.
bi- + linguismo = bilinguismo
bilingualism
tri- + ciclo = triciclo
tricycle
multi- + nacional = multinacional
multinational
poli- + glota = poliglota
polyglot
hiper-, mega-, ultra-
Intensifiers. Productive in pop coinages: hipercalórico, megaprojeto, ultramoderno. Solid, no hyphen in most cases, but hiper- takes a hyphen before h or r under AO90.
Este bolo é hipercalórico — uma fatia tem mais calorias que um almoço.
This cake is hypercaloric — one slice has more calories than a lunch.
A empresa lançou um megaprojeto de habitação.
The company launched a mega-housing project.
semi-
"Half, partly." AO90 hyphen before h or i.
semi- + final = semifinal
semifinal
semi- + círculo = semicírculo
semicircle
semi- + intensivo = semi-intensivo
semi-intensive (double *i*, hyphen)
semi- + humano = semi-humano
semi-human (before *h*, hyphen)
Location: inter-, intra-, extra-, ultra-, trans-
| Prefix | Sense | Example |
|---|---|---|
| inter- | between | internacional, interuniversitário |
| intra- | inside, within | intravenoso, intramuscular |
| extra- | outside, beyond | extracurricular, extraordinário |
| ultra- | beyond, very | ultramoderno, ultravioleta |
| trans- | across | transatlântico, transnacional |
A reunião interuniversitária decorre no próximo mês.
The inter-university meeting takes place next month.
O voo transatlântico atrasou-se duas horas.
The transatlantic flight was delayed by two hours.
A summary table of prefixes and hyphenation
| Prefix | Meaning | Hyphen before | Example pair |
|---|---|---|---|
| des- | un-, dis- | never | desfazer, desumano |
| in-/im-/i-/ir- | not | never (form changes instead) | incapaz, imperfeito, ilegal, irreal |
| a-/an- | not (scientific) | never | anormal, anaeróbio |
| anti- | against | h, i | antibiótico, anti-herói, anti-inflamatório |
| contra- | against, counter | a, h | contradizer, contra-ataque |
| re- | again | never | refazer, reeleger |
| pre- | before (fused Latin) | never | preparar, prever |
| pré- | before (modern) | always | pré-histórico, pré-aviso |
| pós- | after | always | pós-graduação |
| sobre- | above, excess | never | sobrevoar, sobrecarga |
| super- | super, very | h, r | superdotado, super-homem |
| sub- | under | b, h, r | subterrâneo, sub-humano, sub-região |
| auto- | self | h, o | autoestrada, auto-hipnose, auto-observação |
| co- | together | rarely; mostly solid | coautor, coexistir, cooperar |
| ex- | former | always | ex-presidente, ex-marido |
| semi- | half | h, i | semifinal, semi-intensivo |
| hiper- | very, over | h, r | hipertensão, hiper-restritivo |
AO90 changes worth remembering
The Acordo Ortográfico 1990 changed a number of Portuguese spellings. For prefixation, the key changes in PT-PT are:
- Silent consonants dropped: antiprojecto → antiprojeto, adoptar → adotar, excepcional → excecional. This affects prefixed words as much as bare ones.
- Auto-, contra-, extra-, infra-, intra-, neo-, proto-, pseudo-, ultra- before a vowel: fuse solid unless the vowel is the same as the prefix's final vowel. Autoestrada (different vowel, solid), auto-observação (same o, hyphen).
- Co-: fuse solid in almost all cases, even before a vowel or h: coautor, coexistir, coabitar, coordenar. The major exception is some legal set phrases.
- Pós-, pré-, pró-: always hyphenated when autonomous (with accent). Distinguished from fused pós/pre/pro in Latin-origin words (no accent, no hyphen).
Both AO90 and pre-AO90 spellings are mutually intelligible; the test is simply which is the current standard in Portuguese publications and official documents, and the answer is AO90.
Common mistakes
❌ des-honesto
*Des-* never takes a hyphen, even before *h*. One of the few exceptions to the general *h* rule.
✅ desonesto
dishonest
❌ antiherói, antiinflamatório
Under AO90, *anti-* hyphenates before *h* and *i*. *Anti-herói, anti-inflamatório*.
✅ anti-herói, anti-inflamatório
anti-hero, anti-inflammatory
❌ co-autor, co-operar
Pre-2009 spellings. Under AO90, *co-* fuses solid: *coautor, cooperar*.
✅ coautor, cooperar
co-author, to cooperate
❌ auto-estrada
Pre-2009 spelling. AO90 writes it solid: *autoestrada*.
✅ autoestrada
motorway, highway
❌ reescrever (with two e's but hyphen)
Pre-AO90 sometimes used *re-escrever*. The modern spelling is solid: *reescrever*.
✅ reescrever
to rewrite
❌ pré-parar (a verb, treated as modern pré-)
*Preparar* is a Latin-origin verb, fused, unstressed on the prefix. No accent, no hyphen.
✅ preparar
to prepare
❌ expresidente
*Ex-* (meaning former) always takes a hyphen.
✅ ex-presidente
former president
Key takeaways
- Prefixes add meaning to a stem without usually changing its word class.
- The most productive prefixes in modern PT-PT are des- (reversal/negation), re- (repetition), pré- (before, with hyphen and accent), anti- (against), and the Latinate in-/im-/i-/ir- family (negation).
- Hyphenation under the Acordo Ortográfico 1990 is rule-governed: hyphen when the stem begins with the same letter as the prefix ends with, or with h (for most prefixes).
- Exceptions: des- never hyphenates (even before h); re- never hyphenates (even before e); co- almost always fuses solid under AO90.
- Distinguish pre- (fused Latin, no accent, no hyphen: preparar, prever) from pré- (modern, accented, hyphenated: pré-histórico, pré-aviso).
- Ex- (meaning "former") always takes a hyphen: ex-presidente, ex-marido.
- When in doubt, the Portuguese online dictionary Priberam and the Vocabulário Ortográfico Português (VOP) give the AO90-compliant spelling.
Related Topics
- 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.
- Noun-Forming SuffixesB1 — The productive suffixes European Portuguese uses to build nouns — action, abstract quality, agent, collective, place, and evaluative — with the register and gender notes each one carries.
- Adjective-Forming SuffixesB1 — The productive suffixes European Portuguese uses to build adjectives from nouns, verbs, and other adjectives — what each suffix means, what it attaches to, and the register notes that go with it.
- 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).