Causal linking always has two directions. You can point backward to the cause ("we stayed home because it was raining") or forward to the effect ("it was raining, so we stayed home"). English keeps these two jobs cleanly separate — because/since on the cause side, so/therefore on the effect side — and Brazilian Portuguese does exactly the same, but with a richer inventory split sharply by register. This page sorts every common connector into its side and its register so you always reach for the right one.
The cause side: porque, pois, já que, como, por causa de
These connectors introduce the reason. The thing after them is why something happened.
Porque — the default reason (spoken/general)
Porque (one word, no accent) is the everyday because. It introduces a full clause and almost always comes after the main statement:
Não fui trabalhar porque acordei com febre.
I didn't go to work because I woke up with a fever.
A gente cancelou a viagem porque o voo ficou caríssimo.
We canceled the trip because the flight got super expensive.
Don't confuse the four "porques": porque (because), por que (why, in questions), por quê (why, sentence-final), porquê (the noun "the reason"). For causal linking, you want the joined, unaccented porque.
Pois — bookish 'for/since' (written/formal)
Pois introduces a cause in writing and sounds elevated. In speech, pois survives mostly in set phrases (pois é "yeah/right," pois não "of course/may I help you?") rather than as a causal connector:
Adiamos a reunião, pois faltavam dados essenciais.
We postponed the meeting, for essential data were missing.
Já que, visto que, uma vez que — 'since/given that'
These introduce a cause already known to the listener ("since you mention it," "given that we agree"). Já que is neutral and common in speech; visto que and uma vez que are more formal/written:
Já que você tá indo ao mercado, traz pão?
Since you're going to the market, will you bring bread?
Visto que os prazos foram cumpridos, o contrato será renovado.
Given that the deadlines were met, the contract will be renewed.
Como — cause, but only sentence-initial
Como can mean as/since (cause), but only at the start of the sentence. Mid-sentence, como means like/how, not because. This is a real trap:
Como estava chovendo, ficamos em casa.
Since it was raining, we stayed home.
Ficamos em casa como estava chovendo.
(Wrong meaning) — here 'como' reads as 'the way it was raining', not 'because'.
Por causa de, devido a, graças a, em virtude de — cause + noun
When the cause is a noun rather than a clause, use a prepositional phrase:
- por causa de — neutral, "because of"
- devido a — slightly formal, "due to"
- graças a — "thanks to" (positive cause)
- em virtude de, em razão de — formal/legal "by virtue of, owing to"
O voo atrasou por causa do nevoeiro.
The flight was delayed because of the fog.
Graças à sua ajuda, terminamos no prazo.
Thanks to your help, we finished on time.
Em virtude do feriado, o expediente será reduzido.
Owing to the holiday, working hours will be reduced.
The effect side: então, por isso, portanto, logo, assim
These point forward to the result. The thing after them is the consequence.
Então, por isso — the spoken result markers (spoken/general)
In conversation, Brazilians overwhelmingly mark consequences with então ("so") and por isso ("that's why / so"):
Tava chovendo, então a gente ficou em casa.
It was raining, so we stayed home.
Perdi o ônibus, por isso cheguei atrasado.
I missed the bus, that's why I arrived late.
Portanto, logo, por conseguinte — the written result markers (written/formal)
For essays and arguments, the logical-consequence markers are portanto ("therefore"), logo ("hence" — note: not "soon" here), por conseguinte and consequentemente ("consequently"):
Os custos subiram; portanto, o preço final aumentará.
Costs rose; therefore, the final price will increase.
Penso, logo existo.
I think, therefore I am.
A demanda caiu; por conseguinte, a produção foi reduzida.
Demand fell; consequently, production was cut.
Assim, de modo que, de forma que — 'so that / in such a way that'
Assim ("thus/so") and de modo que / de forma que ("so that / such that") express result, the last two often introducing a purpose-tinged consequence:
Ele explicou tudo devagar, de modo que todos entendessem.
He explained everything slowly, so that everyone would understand.
Note the subjunctive (entendessem) when de modo que expresses intended result/purpose; with a plain factual result it stays indicative (de modo que todos entenderam — "so that everyone understood").
Putting it together: matching cause to effect by register
The cleanest way to internalize this is by register pairing:
| Register | Cause side | Effect side |
|---|---|---|
| Spoken | porque, já que, por causa de | então, por isso |
| Written/formal | visto que, uma vez que, devido a, pois | portanto, logo, por conseguinte, consequentemente |
Como o réu confessou e visto que as provas eram robustas, o juiz, por conseguinte, decretou a condenação.
Since the defendant confessed and given that the evidence was robust, the judge consequently ordered the conviction.
That single sentence is unmistakably written/legal — every connector in it sits on the formal rung.
Common Mistakes
❌ Ficamos em casa como chovia.
Incorrect — causal 'como' only works sentence-initially.
✅ Como chovia, ficamos em casa. / Ficamos em casa porque chovia.
Since it was raining, we stayed home. / We stayed home because it was raining.
❌ Não fui por que estava doente.
Incorrect — 'por que' (two words) is for questions; the connector 'because' is one word.
✅ Não fui porque estava doente.
I didn't go because I was sick.
This is the single most common spelling error Brazilians themselves make. Causal because = porque, one word, no accent.
❌ Estava chovendo, por isso que ficamos em casa.
Colloquial — 'por isso que' is heard in speech but flagged in writing.
✅ Estava chovendo, por isso ficamos em casa.
It was raining, that's why we stayed home.
The spoken por isso que (with stray que) is everywhere in conversation but considered incorrect in careful writing — drop the que.
❌ O voo atrasou por causa de o nevoeiro.
Incorrect — 'por causa de' must contract with the article: de + o = do.
✅ O voo atrasou por causa do nevoeiro.
The flight was delayed because of the fog.
❌ Penso, então existo.
Register mismatch — for a formal logical conclusion use 'portanto/logo', not the casual 'então'.
✅ Penso, logo existo.
I think, therefore I am.
In a logical argument or a maxim, então sounds too chatty; reach for logo or portanto.
Key Takeaways
- Causal linking has two sides: cause (porque, já que, como, por causa de, devido a) and effect (então, por isso, portanto, logo, por conseguinte).
- Speech leans on porque ... então / por isso; writing uses visto que / uma vez que ... por conseguinte / portanto.
- Causal como only works at the start of the sentence.
- Watch the homophones and contractions: porque (one word) for cause, por causa do (contracted), and logo = therefore (not "soon") when it links clauses.
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