Por ejemplo, se usa subjuntivo después de "cuando", para expresar ideas futuras:
- (yo) Iré al cine cuando (yo) tenga tiempo suficiente I will go to the cinema when I have enough time
Después de "si" se usa para frases condicionales que expresen una situación hipotética:
- Si yo fuera rico..If I were a rich man.. (I am not a rich man, so it's an hipotetical situation)
- (yo) Iría al cine si (yo) tuviera tiempo. I will go to the cinema if I had enough time (It's an hipotetical situation because it's sure I have no time --> PAST SUBJUNCTIVE)
- (yo) Iré al cine si tengo tiempo suficiente. I will go to the cinema if I have enough time (It's likely I have time so it's not an hipotetical situation --> PRESENT)
También se usa subjuntivo después de "si" para expresar un deseo del pasado sobre algo que no ocurrió
- (yo) Habría ido al cine si (yo) hubiera tenido dinero I'd have gone to the cinema if I had had enough time (I didn't have time and I didn't go, but I would like to go --> PAST PERFECT SUBJUNCTIVE)
Espero haberte aclarado algo.