If Sentences

1. Present Factual

Si + present indicative, future

e.g. Si estudio, aprenderé. = If I study, I will learn.
e.g. Si trabajo, voy a ganar dinero. = If I work, I am going to earn money.

2. Present Hypothetical

Si + imperfect subjunctive, conditional

e.g. Si estudiara/estudiase, aprendería. = If I studied, I would learn.

alternate form: Si + imperfect subjunctive, imperfect subjunctive (only RA)

e.g. Si estudiara/estudiase, aprendiera.

3. Past Hypothetical

Si + past perfect subjunctive, conditional perfect

e.g. Si hubiera/hubiese estudiado, habría aprendido. = If I had studied, I would have learned.

alternate form: Si + past perfect subjunctive, past perfect subjunctive (only RA)

e.g. Si hubiera/hubiese estudiado, hubiera aprendido.

4. Other possibilities

Si + indicative mood, logical conjugation

e.g. Si el doctor no llega, llámame. = If the doctor doesn’t arrive, call me.

5. Hypothetical if sentences can be constructed in the following ways:

Si + imperfect subjunctive (RA or SE form), imperfect subjunctive (only RA form)

e.g. Si tuviera/tuviese más tiempo, estudiara más.

Si + past perfect subjunctive (RA or SE form), past perfect subjunctive (only RA form)

e.g. Si hubiera/hubiese tenido más tiempo, hubiera estudiado más.