English uses a certain in two distinct ways: a certain man (someone specific whose name I am withholding) and a certain kind (a particular type). Portuguese has two determiners that cover this semantic space — certo and determinado — with a subtle register difference. But certo has a further trick: put it after the noun and it stops meaning certain and starts meaning correct. The same word, two radically different senses, distinguished only by position. This page teaches you to read the position, choose the right determiner, and avoid the errors that come from English and Spanish interference.
Certo / certa / certos / certas — position changes meaning
Certo agrees in gender and number with its noun:
| Masculine | Feminine | |
|---|---|---|
| Singular | certo | certa |
| Plural | certos | certas |
But the agreement is the easy part. The hard part is the position rule, which acts like a semantic switch:
- Before the noun: certa pessoa = a certain person (indefinite identity)
- After the noun: a pessoa certa = the right / correct person
This is not a stylistic variation. It is two different words that happen to share the same form, differentiated only by where they sit.
Pre-nominal certo — "a certain" (indefinite)
Before the noun, certo signals that you have a specific referent in mind, but are deliberately leaving it unnamed or vague. It is roughly "some, a particular" with a hint of mystery or reticence.
Certa pessoa disse-me que tu ias mudar de emprego.
A certain person told me you were going to change jobs.
Por certos motivos, não posso contar-te.
For certain reasons, I can't tell you.
Houve um certo mal-entendido entre eles.
There was a certain misunderstanding between them.
Ela tem um certo encanto.
She has a certain charm.
Notice how the English translations all preserve the slight indeterminacy of the Portuguese — a certain misunderstanding (we don't specify which), for certain reasons (we won't say what).
Pre-nominal certo can optionally take um/uma — um certo mal-entendido — without changing meaning. The bare certo mal-entendido is grammatical but slightly more literary.
Certo dia, encontrei-a na rua.
One day / a certain day, I met her in the street. (literary/narrative)
Num certo dia, encontrei-a na rua.
One day, I met her in the street. (neutral)
Post-nominal certo — "correct, right"
After the noun, certo is no longer indefinite. It means correct, right, accurate — and typically takes a definite article before the noun.
A resposta certa é a letra B.
The correct answer is letter B.
A hora certa para ligar é depois do jantar.
The right time to call is after dinner.
Escolheste o presente certo.
You chose the right gift.
As medidas certas estão no manual.
The correct measurements are in the manual.
The two uses are not just semantically different — they are syntactically different. Pre-nominal certo patterns with other indefinite determiners (algum, qualquer, vário). Post-nominal certo patterns with qualifying adjectives (bom, bonito, grande).
Side-by-side comparison
Certas respostas deixam muito a desejar.
Certain answers leave much to be desired. (some particular ones)
As respostas certas estão no fim do livro.
The correct answers are at the end of the book.
Faz a escolha certa.
Make the right choice.
Certo indivíduo apresentou uma queixa.
A certain individual filed a complaint.
Ele é o indivíduo certo para o cargo.
He's the right individual for the position.
Read these pairs slowly. The switch is entirely in the position, and the meaning changes completely.
Determinado / determinada / determinados / determinadas — "a specific, particular"
Determinado is a more formal alternative to pre-nominal certo. It agrees in gender and number. Its core meaning is particular, specific, identified but unnamed.
| Masculine | Feminine | |
|---|---|---|
| Singular | determinado | determinada |
| Plural | determinados | determinadas |
Pre-nominal determinado — "a specific, a particular"
Placed before the noun, determinado indicates a specific, identified referent that you are deliberately not naming. It is close in meaning to pre-nominal certo, but slightly more specific and distinctly more formal.
Por determinadas razões, não posso comentar o caso.
For specific reasons, I cannot comment on the case.
Num determinado momento, perdi a paciência.
At a particular moment, I lost my patience.
Determinados autores defendem uma outra teoria.
Certain (specific) authors defend another theory.
Em determinadas situações, a lei permite exceções.
In certain situations, the law allows exceptions.
Ele só responde a determinadas perguntas.
He only answers certain questions.
Determinado belongs to written, formal, and semi-formal registers — legal writing, academic prose, journalism, careful speech. In a casual conversation at a café, certo would sound more natural. In an essay or a contract, determinado is often preferred.
Post-nominal determinado — "determined, set, fixed" (less common)
Post-nominal determinado does exist but is rare. It means determined in the sense of decided, established, fixed — typically applied to times, dates, amounts.
Temos uma data determinada para a reunião.
We have a set date for the meeting.
Por uma quantia determinada, ele aceita o trabalho.
For a determined (fixed) amount, he accepts the job.
Não há um número determinado de candidatos.
There is no fixed number of candidates.
This use is much rarer than pre-nominal determinado. In everyday usage, you will meet determinado mostly before the noun.
Certo vs. determinado — choosing between them
Both determiners can express "a certain" in the sense of "some specific but unnamed." They are not identical.
| Feature | certo | determinado |
|---|---|---|
| Register | Neutral — fine in speech | Formal — written, academic, legal |
| Degree of specificity | Slightly vaguer | More specific, identified-but-unnamed |
| Position effect | Pre = "a certain"; Post = "correct" | Pre = "a specific"; Post (rare) = "fixed, set" |
| Default position | Before the noun (for "certain"); after for "correct" | Almost always before the noun |
| Frequency | Very common | Common in formal contexts |
Certa pessoa telefonou para ti.
A certain person called you. (neutral — everyday speech)
Determinada pessoa manifestou interesse no cargo.
A specific (particular) person expressed interest in the position. (formal — appropriate in a workplace context)
Em certos casos, é melhor esperar.
In certain cases, it's better to wait. (neutral)
Em determinados casos, a lei autoriza exceções.
In specific cases, the law authorises exceptions. (formal)
If you are writing a report, use determinado. If you are chatting with a friend, use certo. Neither is wrong in the other context — they just sound register-marked when swapped.
Comparison with tal — "such"
Tal is another determiner in the same semantic neighbourhood. It means such — referring to a type or kind rather than a specific but unnamed individual.
Certa pessoa está à tua procura.
A certain person is looking for you. (unnamed but specific)
Determinada pessoa está à tua procura.
A specific person is looking for you. (formal)
Tal pessoa não existe.
Such a person doesn't exist. (that kind / that type of person)
Nunca ouvi tal coisa!
I've never heard such a thing!
Tal is more about the type or kind; certo and determinado are about identity (withheld). They are not interchangeable, though they sometimes cluster in the same sentence position.
Fixed expressions with certo
Em certo sentido, tens razão.
In a certain sense, you're right.
Estou certo de que ela vem.
I'm sure she's coming. (certo as a predicate adjective — 'sure')
Ao certo, não sei a que horas chegam.
I don't know exactly when they arrive. (ao certo = 'for certain, exactly')
Isto é caso certo.
This is a sure thing.
De certo modo, tens razão.
In a certain way, you're right.
Notice that estar certo (to be sure) uses certo as a predicate adjective — a different grammatical role from the determiner we have been discussing.
Fixed expressions with determinado
Num determinado momento da minha vida, mudei de cidade.
At a certain point in my life, I moved cities.
A partir de determinada idade, começas a valorizar o silêncio.
From a certain age, you start to value silence.
Sob determinadas condições, o acordo é válido.
Under specific conditions, the agreement is valid.
Em determinadas circunstâncias, a regra aplica-se.
In specific circumstances, the rule applies.
Comparison with English
English a certain is actually two words pretending to be one:
- I know a certain man → Portuguese certo homem / um certo homem (indefinite identity)
- The certain answer → this is wrong in English; English doesn't use certain post-nominally in this sense
Portuguese splits the semantic territory differently. Certo X = "a certain X" (pre-nominal). X certo = "the correct X" (post-nominal). There is no overlap. English learners who translate certain literally without checking position routinely mangle this.
Comparison with Spanish
Spanish cierto (cognate of certo) behaves mostly in parallel — pre-nominal for "a certain," post-nominal for "correct." Spanish determinado also parallels Portuguese. The risk for Spanish speakers is subtler:
- Spanish often uses determinado more heavily than Portuguese in everyday speech.
- PT-PT tends to prefer certo in informal contexts; Spanish more readily uses determinado.
Don't overuse determinado in casual Portuguese — it will sound bureaucratic. Stick with certo unless the register calls for formal weight.
Register notes
- (neutral) Pre-nominal certo: everyday speech and writing.
- (neutral) Post-nominal certo (= correct): everyday speech and writing.
- (formal / academic / legal) Pre-nominal determinado: formal writing, academic prose, contracts, journalism.
- (rare) Post-nominal determinado (= fixed, decided): mostly in specific contexts — schedules, quantities.
- (idiomatic / adjectival) Estar certo (to be sure), ao certo (for sure) — different use of certo as predicate adjective.
Common Mistakes
❌ Ela deu a certa resposta.
Position reversed — pre-nominal 'certa' means 'a certain', which doesn't fit here. For 'the correct answer', use post-nominal.
✅ Ela deu a resposta certa.
She gave the correct answer.
❌ A pessoa certa telefonou — não sei quem era.
Ambiguous/wrong — 'a pessoa certa' means 'the right person', not 'a certain person'. For 'a certain person', use pre-nominal.
✅ Certa pessoa telefonou — não sei quem era.
A certain person called — I don't know who it was.
❌ Determinados dias, fico em casa.
Too formal for casual speech — use 'em certos dias' in conversation.
✅ Em certos dias, fico em casa.
On certain days, I stay home. (neutral register)
✅ Em determinados dias, o serviço está indisponível.
On certain (specific) days, the service is unavailable. (formal — e.g. in a notice)
❌ É uma decisão certo.
Agreement error — 'decisão' is feminine, so 'certa'.
✅ É uma decisão certa.
It's the right decision.
❌ Por razões certas, não posso explicar.
Post-nominal gives wrong reading — 'razões certas' = 'correct reasons', not 'certain reasons'.
✅ Por certas razões, não posso explicar.
For certain reasons, I can't explain.
❌ Ele é o certo homem para o cargo.
Wrong position — post-nominal 'certo' means 'correct', so 'o homem certo' is needed.
✅ Ele é o homem certo para o cargo.
He's the right man for the position.
❌ Tal a resposta não é aceitável.
Incorrect — 'tal' does not take the article between it and the noun.
✅ Tal resposta não é aceitável.
Such an answer is not acceptable.
Key Takeaways
- Certo has two meanings determined by position: pre-nominal = a certain (indefinite identity); post-nominal = correct, right.
- Determinado is a more formal pre-nominal synonym for "a certain" — appropriate for academic, legal, or careful writing. Avoid in casual speech.
- Both determiners agree in gender and number with the noun: certo/certa/certos/certas, determinado/determinada/determinados/determinadas.
- Position test for certo — if the meaning is a particular, some unnamed, put it before the noun. If the meaning is correct, right, put it after the noun.
- Pre-nominal certo can take um/uma optionally (um certo homem = certo homem).
- Post-nominal certo typically takes the definite article (o livro certo, a resposta certa).
- Tal covers a different semantic space — "such, that kind of" — and is not interchangeable with certo or determinado.
- Register guideline: neutral → certo; formal → determinado.
- Estar certo (to be sure) and ao certo (exactly, for certain) use certo as a predicate adjective, not a determiner.
- English speakers routinely drop the position rule — check every time: "is this 'a certain' or 'the correct'?"
Related Topics
- Determiners in Portuguese: An OverviewA1 — What determiners are, the families of determiners in European Portuguese, and how they combine with nouns — a map of the group.
- Indefinite Determiners: algum, nenhum, qualquer, cada, todo, vário, certoA2 — A guided tour of the Portuguese indefinite determiners — words that quantify or identify without being definite: algum, nenhum, qualquer, cada, todo, vário, certo, muito, pouco, outro, mesmo, tanto, and the todo/tudo distinction.
- The Indefinite Article: Forms and UsesA1 — The four forms of the Portuguese indefinite article (um, uma, uns, umas), their uses for introducing new referents, and where Portuguese drops the article that English keeps.
- Indefinite Pronouns (Alguém, Ninguém, Algo, Nada, Tudo)A2 — Referring to unspecified people and things — someone, no one, something, nothing, everything