When the past condition is real
Si + hubiera + participle imagines a past that did not happen. Very often, though, the condition is something you take as true, or as quite possibly true: you draw a conclusion from it, ask why, or tell someone what to do. Then si simply takes a past tense of the indicative.
| real: indicative | imagined: subjunctive |
|---|---|
| Si lo sabías, ¿por qué no me lo dijiste? | Si lo hubiera sabido, te habría llamado. |
| you knew, so why the silence? | I didn't know |
| If you knew, why didn't you tell me? | Si lo sabías, ¿por qué no me lo dijiste? |
A reproach: the speaker is sure you knew.
| If I had known, I would have called you. | Si lo hubiera sabido, te habría llamado. |
Drawing a conclusion
After a real past condition, the result is often a guess with the future or the conditional of probability, or a question.
| If she arrived yesterday, she must be very tired. | Si llegó ayer, estará muy cansada. |
| If he didn't come to the wedding, he probably had his reasons. | Si no vino a la boda, tendría sus razones. |
With the present perfect
Si + present perfect looks at something that may already have happened. The result can be a guess, a piece of advice or an order.
| If he has called, he will have left a message. | Si ha llamado, habrá dejado un mensaje. |
| If you have already finished, you can leave. | Si ya has terminado, puedes irte. |
The preterite works the same way, for an event in a finished past time:
| If you saw something, tell me. | Si viste algo, dímelo. |
Habits: si + imperfect
Si + imperfect, with an imperfect in the result, tells what used to happen whenever something was the case. It is close to cuando.
| As a child, if it rained, I stayed at home reading. | De pequeño, si llovía, me quedaba en casa leyendo. |
| My grandmother, if she could, went to the market every day. | Mi abuela, si podía, iba al mercado todos los días. |
Common mistakes
- After si meaning if, Spanish normally doesn't use the future: Si habrá llamado → Si ha llamado.
- Nor the present subjunctive: Si lo sepas → Si lo sabes / Si lo sabías.
