Os três degraus do se
Conditional sentences come on three rungs, and each rung locks its two verbs together. Rung 1, real: Se chove, eu fico em casa — and pointed at the future, Se chover amanhã, eu fico em casa. Rung 2, hypothetical: Se eu tivesse tempo, eu iria com você. Rung 3, counterfactual — it didn't happen: Se eu tivesse estudado, eu teria passado. Work out which rung you're standing on and the verbs pick themselves. One rule never bends: after se you never use the presente do subjuntivo from lesson 26. Se ele venha is not a sentence in any variety of Portuguese.
Rung 1 — real conditions: se + presente do indicativo
When the condition might genuinely be true, both halves stay in the indicative, even though English says 'if'. Se chove, eu fico em casa. Se você tem tempo, a gente vai ao mercado. Se ele está doente, não vem trabalhar. Now the part that makes Brazilian ears prick up: when se points at the FUTURE, Portuguese has a tense of its own for it — the futuro do subjuntivo, and unlike in many languages it is completely alive here. Se chover amanhã, eu fico em casa. Se você quiser, a gente vai junto. Se eu puder, eu te ligo. Se Deus quiser is the same tense, frozen into a blessing. Build it from the eles form of the pretérito perfeito minus -am: falaram → falar, comeram → comer, partiram → partir — for regular verbs it's a twin of the infinitive, which is why you never noticed it. The irregulars are where you see it working: fizeram → fizer, tiveram → tiver, puderam → puder, quiseram → quiser, disseram → disser, foram → for, vieram → vier, souberam → souber, trouxeram → trouxer. The same tense follows quando, assim que, enquanto and depois que with future meaning: Quando eu chegar, eu te aviso.
Rung 2 — hypothetical: se + imperfeito do subjuntivo
For situations that aren't true but are imaginable — if I had time, if I were rich — the se clause takes the imperfeito do subjuntivo and the other half takes the condicional. Formation is mechanical: take the eles form of the pretérito perfeito, cut -ram, add -sse. falaram → fala- → falasse, falasse, falássemos, falassem. comeram → comesse. partiram → partisse. Every irregular preterite you learned in lesson 17 pays off again: foram → fosse, tiveram → tivesse, fizeram → fizesse, puderam → pudesse, souberam → soubesse, vieram → viesse, disseram → dissesse, quiseram → quisesse, estiveram → estivesse, trouxeram → trouxesse. Se eu tivesse tempo, eu iria com você. Se ela soubesse a verdade, ela ligaria para você. You already met tivesse, pudesse and fosse as ready-made chunks back in lesson 21 — this is the machine that makes them.
Rung 3 — counterfactual: se + mais-que-perfeito do subjuntivo
For what did NOT happen, stack tivesse with a past participle, and answer with teria plus a participle. Se eu tivesse estudado mais, eu teria passado no exame. Se a gente tivesse saído mais cedo, não teria perdido o ônibus. Se você tivesse me falado, eu teria ajudado — and notice me sitting in front, where Brazil keeps it. The participle doesn't agree with anything here; it just sits there: estudado, falado, comido, partido, plus the irregulars feito, dito, visto, posto, aberto, escrito. The auxiliary is ter in the imperfeito do subjuntivo — tivesse, tivesse, tivéssemos, tivessem. (You'll see houvesse doing the same job in formal writing; you don't need to produce it.)
Mixing the rungs — and what NOT to mix
The safe pairings: rung 1 is se + presente or futuro do subjuntivo, answered by the present or by vou + infinitive. Rung 2 is se + imperfeito do subjuntivo, answered by the condicional. Rung 3 is se tivesse + participle, answered by teria + participle. Now the prohibition worth tattooing somewhere: se never, ever takes the presente do subjuntivo. Not se ele venha — it's se ele vem (real), se ele vier (future), se ele viesse (hypothetical). If you want 'maybe', that's talvez plus the subjunctive, a different construction entirely. Crossing rungs on purpose is fine when the meaning asks for it: Se eu tivesse estudado medicina, hoje eu seria médico — a past condition with a present result, and a perfectly normal sentence.
Brazilian register: speech crowds out writing
Spoken Brazilian shaves a rung wherever it can. The condicional in rung 2 slides into the imperfeito almost by default: Se eu tivesse tempo, eu ia com você. Se eu fosse rico, comprava uma casa na praia. Rung 3 flattens the same way — Se eu tivesse estudado, eu tinha passado, or even eu passava. All of these are normal, warm, educated speech; keep iria, compraria and teria passado for anything you write down. The place where Brazilian speech is stricter than learners expect is the futuro do subjuntivo: nobody says se eu posso ir amanhã, everybody says Se eu puder ir amanhã. The slips you'll hear are inside the irregulars — se eu poder, quando eu ver ela — where the careful forms are se eu puder and quando eu vir. And one formula to memorize whole, because you'll want it every week: Se eu fosse você… = if I were you…
