The standard structure is:
| Time reference | Verb in main clause | Verb in conditional clause | ||
|
Present or future |
would, (could, might) |
Past, usually past simple |
 | If you won a fortune, what would you do? (Si ganaras una fortuna, ¿qué harías?) |
| We wouldn't be surprised if there was a strike. (No nos sorprendería que hubiera una huelga.) |
| If Jane came, she might be able to help us. (Si viniera Jane, tal vez nos podría ayudar.) |
| If your cousins were staying longer, we could visit the mountains. (Si vuestros primos se quedaran más tiempo, podríamos ir a la montaña.) |
You will sometimes meet second conditionals with a different structure including should, e.g.:
| If you should win a fortune, what would you do? (Si ganaras una fortuna, ¿qué harías?) |
There are variant conditional structures, which are less frequent, but which have a similar meaning, e.g.:
| If you were to win a fortune, what would you do? (Si ganaras una fortuna, ¿qué harías?) |
| If you should win a fortune, what would you do? (Si ganaras una fortuna, ¿qué harías?) |
| Were you to win a fortune, what would you do? (Si ganaras una fortuna, ¿qué harías?) |
| Should you win a fortune, what would you do? (Si ganaras una fortuna, ¿qué harías?) |
| Supposing (that) you won a fortune, what would you do? (Suponiendo que ganaras una fortuna, ¿qué harías?) |
These variants usually suggest a more improbable condition.
Just as in Spanish, the condition is not always made explicit, e.g.:
| I wouldn't live there for all the money in the world. (No viviría allí ni por todo el dinero del mundo.) |
| But for John's courage, we would all be dead. (Si no fuera por la valentía de John, estaríamos todos muertos.) |
We also use would rather and it's time with a past verb form that refers to present or future time, e.g.:
| A: Is it all right if the representative comes this afternoon? (¿Va bien si el representante viene esta tarde?) |
| B: I'd rather he came tomorrow. (Preferiría que vinieras mañana.) |
| It's late. It's time we went home. (Es tarde. Es hora de irnos a casa.) |
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