Conditional conjunctions set up an "if" relationship: clause B happens only under the condition described in clause A. The challenge for English speakers is that Portuguese chooses the verb mood according to what kind of condition it is — real, open-future, or hypothetical — and different conjunctions lock in different moods. Get the mood wrong and the sentence either changes meaning or sounds plainly foreign.
se — the chameleon: three conditions, three moods
Se ("if") is the workhorse conditional conjunction, and unlike most others it is not tied to a single mood. Instead, the mood depends on how real the condition is. This is the most important table on the page.
| Condition type | Mood after se | Example |
|---|---|---|
| Real / habitual (general truth) | indicative (present) | Se chove, fico em casa. |
| Open future (likely, "if/when") | future subjunctive | Se chover, vou ficar em casa. |
| Hypothetical / counterfactual | imperfect subjunctive | Se chovesse, eu ficaria em casa. |
Real conditions — indicative
When the condition is a general truth or a recurring fact, both clauses stay in the indicative. English does the same with the present simple ("If it rains, I stay home").
Se chove, eu fico em casa.
If (whenever) it rains, I stay home.
Se você mistura azul e amarelo, dá verde.
If you mix blue and yellow, you get green.
Open-future conditions — the future subjunctive
Here is where Portuguese diverges sharply from English. When the "if" points to a specific possible future event, Portuguese uses the future subjunctive after se — a tense that English does not have at all. English just uses the present ("if it rains tomorrow"), which is exactly the trap: learners carry over the present indicative and produce errors.
Se chover amanhã, a gente cancela o piquenique.
If it rains tomorrow, we'll cancel the picnic.
Se eu puder, te ligo mais tarde.
If I can, I'll call you later.
Se você vir o João, manda um abraço meu.
If you see João, send him my regards.
Note the irregular future subjunctive forms: puder (poder), vir (ver), for (ser/ir), tiver (ter). These are built from the third-person plural preterite stem, not from the infinitive — eles puderam → puder.
Hypothetical conditions — the imperfect subjunctive
When the condition is unlikely, imaginary, or contrary to fact, se takes the imperfect subjunctive, and the result clause uses the conditional (or, colloquially, the imperfect indicative).
Se eu pudesse, viajaria o mundo inteiro.
If I could, I'd travel the whole world.
Se eu fosse você, não assinaria esse contrato.
If I were you, I wouldn't sign that contract.
Se chovesse agora, a gente nem ia conseguir sair.
If it were raining now, we wouldn't even be able to leave. (colloquial result in imperfect)
caso — always the present subjunctive
Caso ("if / in case") is a clean rule with no exceptions: it always takes the present subjunctive. It is slightly more formal than se and emphasizes a possible-but-not-assumed scenario. Because the mood is fixed, many learners find caso easier than se.
Caso chova, levamos o guarda-chuva.
In case it rains, we'll take the umbrella.
Caso você precise de algo, é só me avisar.
In case you need anything, just let me know.
Caso não dê certo, a gente tenta de novo.
If it doesn't work out, we'll try again.
Notice the parallel: se chover (future subjunctive) and caso chova (present subjunctive) both describe an open future, but each conjunction demands its own mood. They are interchangeable in meaning, not in grammar.
a menos que / a não ser que — "unless" (+ subjunctive)
"Unless" is a negative condition ("if... not"), and in Portuguese it forces the subjunctive (present subjunctive for present/future reference). Both a menos que and a não ser que work the same way.
Não vou à festa, a menos que você vá comigo.
I'm not going to the party unless you go with me.
A reunião está mantida, a não ser que chova muito.
The meeting is on, unless it rains heavily.
English "unless" + present indicative ("unless you go") maps to a subjunctive in Portuguese, which is the recurring transfer error.
contanto que / desde que — "provided that" (+ subjunctive)
These introduce a condition that must be satisfied — "as long as / provided that" — and also take the subjunctive.
Eu te empresto o carro, contanto que você devolva com o tanque cheio.
I'll lend you the car, provided you return it with a full tank.
Pode usar meu computador, desde que não mexa nos meus arquivos.
You can use my computer, as long as you don't touch my files.
Desde que ele chegou, tudo melhorou.
Ever since he arrived, everything has improved. (temporal — indicative)
Salvo se ("except if") is a (formal) alternative to "unless," common in legal and administrative writing; it takes the indicative or subjunctive depending on the condition type, like se.
O prazo é improrrogável, salvo se houver caso fortuito.
The deadline cannot be extended, except if there is an act of God. (formal)
Common Mistakes
❌ Se você pode, me liga mais tarde.
Incorrect — a future possibility needs the future subjunctive after 'se'.
✅ Se você puder, me liga mais tarde.
If you can, call me later.
❌ Caso chove, levamos guarda-chuva.
Incorrect — 'caso' always takes the present subjunctive, never the indicative.
✅ Caso chova, levamos guarda-chuva.
In case it rains, we'll take an umbrella.
❌ Não vou, a menos que você vai comigo.
Incorrect — 'a menos que' (unless) requires the subjunctive.
✅ Não vou, a menos que você vá comigo.
I'm not going unless you go with me.
❌ Se eu seria você, não faria isso.
Incorrect — the 'se' clause takes the imperfect subjunctive (fosse), not the conditional.
✅ Se eu fosse você, não faria isso.
If I were you, I wouldn't do that.
Key Takeaways
Sepicks its mood by condition type: indicative (real/habitual), future subjunctive (open future —se chover,se eu puder), imperfect subjunctive (hypothetical —se chovesse,se eu fosse).Casois invariant: always present subjunctive (caso chova).- "Unless" (
a menos que,a não ser que) and "provided that" (contanto que,desde que) force the subjunctive. Desde quemeans "provided that" with the subjunctive but "ever since" with the indicative.- The classic English-speaker trap is using the present indicative for a future "if" — Portuguese needs the future subjunctive there.
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Start learning Portuguese→Related Topics
- Conditional Sentences: OverviewB1 — A map of Brazilian Portuguese conditional sentences — real, hypothetical-present, and counterfactual-past 'se' clauses, plus non-'se' conditionals like 'caso' and 'a menos que'.
- Conjunctions and Mood SelectionB1 — The master table mapping each Brazilian Portuguese conjunction to the mood it governs — indicative, subjunctive, or future subjunctive — and the assertion principle that predicts them all.
- Futuro do Subjuntivo: UsageA2 — When to use the future subjunctive in Brazilian Portuguese — the obligatory form after 'quando', 'se', 'enquanto', 'assim que' and other time conjunctions pointing to the future.
- The Subjunctive in BR Portuguese: OverviewA2 — What the subjunctive is, why Brazilian Portuguese keeps all three of its tenses fully alive, and what triggers it.
- Concessive Conjunctions (Embora, Mesmo Que)B1 — How embora, ainda que, mesmo que, por mais que and nem que all take the subjunctive — and why apesar de is a preposition, not a conjunction.