"If it rains, we'll stay home." "If I were rich…" "If I had known…" Every language needs a way to talk about conditions and imagined worlds, and Spanish organises them into three clean patterns. The trick is simple: the tense you choose in the si-clause tells your listener how likely — or how impossible — the situation is.
An si-clause has two halves: the condition (the si part) and the result. Which tenses go in each half depends on whether the situation is real, unreal now, or unreal in the past.
| Type | Si-clause (condition) | Result clause | Feel |
|---|---|---|---|
| 1. Real / likely | si + present indicative | present or future | could really happen |
| 2. Unreal (present) | si + imperfect subjunctive | conditional | imaginary / contrary to fact now |
| 3. Unreal (past) | si + pluperfect subjunctive | conditional perfect | too late, it didn't happen |
Never put the present subjunctive or the conditional directly after si meaning "if." After si you use either the present indicative (type 1) or a past subjunctive (types 2 and 3) — never *si tendría, never *si tenga.
For things that can genuinely happen, keep it grounded: si + present indicative, and in the result use the present or, more often, the future.
Si llueve, nos quedamos en casa. — If it rains, we stay home.
Si estudias, aprobarás el examen. — If you study, you'll pass the exam.
Si tienes tiempo, llámame. — If you have time, call me. (result can even be a command)
Now we step into the imaginary: things that are not true right now, or are unlikely. Use si + imperfect subjunctive in the condition, and the conditional in the result. This is the "If I were… I would…" pattern.
The imperfect subjunctive is built from the ellos form of the preterite: drop -ron and add the endings -ra, -ras, -ra, -ramos, -rais, -ran (a -se set also exists and means the same).
| Verb | ellos preterite | imperfect subjunctive (yo) |
|---|---|---|
| hablar | hablaron | hablara |
| tener | tuvieron | tuviera |
| ser / ir | fueron | fuera |
| poder | pudieron | pudiera |
Si tuviera dinero, viajaría por el mundo. — If I had money, I would travel the world.
Si fuera tú, hablaría con ella. — If I were you, I would talk to her.
¿Qué harías si pudieras vivir en otro país? — What would you do if you could live in another country?
Here we regret or reimagine what already happened. It didn't go that way, but what if it had? Use si + pluperfect subjunctive (hubiera + participle) in the condition, and the conditional perfect (habría + participle) in the result. This is where Lesson 12 pays off.
| Half | Structure | Example piece |
|---|---|---|
| Condition | si + hubiera/hubieras… + participle | si hubiera sabido |
| Result | habría/habrías… + participle | habría venido |
Si hubiera sabido, habría venido antes. — If I had known, I would have come sooner.
Si hubiéramos salido temprano, no habríamos perdido el vuelo. — If we had left early, we wouldn't have missed the flight.
Ella habría ganado si hubiera entrenado más. — She would have won if she had trained more.
Como si ("as if") always takes a past subjunctive, however present the sentence feels: Habla como si lo supiera todo. — He talks as if he knew everything. And ojalá + imperfect subjunctive is a heartfelt wish: Ojalá pudiera ayudarte. — I wish I could help you.
Decide the type, then build the sentence. Say each aloud.
Model answers: Si vienes, comemos juntos. / Si tuviera más tiempo, leería más. / Si hubieran llamado, habría contestado. / Ojalá fuera viernes.
Either half can come first; when the si-clause leads, mark the break with a comma: Si puedo, iré = Iré si puedo. In speech and headlines you'll also hear the compact de + infinitive shortcut for the past-unreal type: De haberlo sabido, habría actuado distinto — Had I known it, I'd have acted differently. It sounds polished, but the full si hubiera… version is always safe.
Likely conditions: si + present, then present/future.
Unreal conditions: si + imperfect/pluperfect subjunctive.