How can I use 'IF' phrases/'SI' clauses?

These 'if' phrases or 'si' clauses in Spanish are sometimes tricky to understand but can really boost your essay or oral exams. They aren't complicated to use once you understand them and can help to get that variety of tenses into your work. 

There are 3 main set-ups for using this structure. 

1. Present indicative 

This is when the condition is taking place in the present and the result of the condition will also either be in the present or the future. 

The structure is SI + present indicative + present/future/imperative 

So, as an example:

Si llueve, no vamos a la playa 

Translation as: If it rains, we will not go to the beach.

As you can see, the first verb, llover - to rain, is in the present and the result, going to the beach, is in the future. 

2. Past Subjunctive 

This second structure is slightly more complex and is used in circumstances when the condition is not true. The condition is therefore past and subjunctive and the result is conditional, since it is not true. 

The structure is SI + imperfect subjunctive + conditional 

For example,

Si yo fuera estudiante de ciencias, yo sería muy triste. 

Translated as: If I were a science student, I would be very unhappy 

And the verb ser is in the past subjunctive (fuera) and is used again in the conditional at the end (sería). 

3. Pluperfect Subjunctive 

Lastly, the third structure is used when past fact is false in comparison to Structure 2 where present fact is false. So the condition is one step behind the past so is still subjunctive but also pluperfect and the result is still conditional but in the past.

The structure is: SI + pluperfect subjunctive + past conditional 

This becomes more clear with an example. 

Si yo hubiera tenido más dinero, yo habría ido de compras.

Translation: If I had had more money, I would have gone shopping.

It describes something that could or would have happened if something else had happened too. 

We see huberia tenido in the pluperfect subjunctive and habría ido is the past conditional. 

Hopefully this makes this often confused but very useful structure a little clearer! My advice would be to just keep practising. Perhaps aim to write out 10-15 phrases for each of the 3 structures to really make sure they are clear in your mind :)