Conditional sentences (with si)
Spanish has three types of 'if' sentences: real (if it rains tomorrow, I'll stay home), unreal present (if I had time, I'd travel), and unreal past (if I had known, I would've gone). Today: the first two — by far the most common. Key idea: after si, strict rules.
Type 1 — real condition
Si + present, … present / futuro / imperative. Si tengo tiempo, voy a tu casa (if I have time, I'll come to your place). Si llueve mañana, me quedaré en casa (if it rains tomorrow, I'll stay home). Si quieres, ven con nosotros (if you want, come with us). After si — PRESENT, not futuro!
Type 2 — unreal present (if I were to…)
Si + imperfect subjunctive, … conditional. Si tuviera tiempo, viajaría a España (if I had time, I'd travel to Spain). The subjuntivo is a new form; for most verbs: take their ellos form in indefinido (tuvieron, hablaron, comieron) and replace the ending with -a, -as, -a, -amos, -ais, -an: tuviera, hablara, comiera.
Imperfect subjunctive — three quick steps
Step 1: take the ellos form of the indefinido. comieron, hablaron, vivieron, fueron, tuvieron. Step 2: drop -ron. comie-, habla-, vivie-, fue-, tuvie-. Step 3: add -ra, -ras, -ra, -ramos, -rais, -ran. comiera, hablara, viviera, fuera, tuviera. Hint: if you know the indefinido, you already know the imperfect subjunctive.
Type 1 vs Type 2
Si tengo dinero, compro un libro = I might actually buy it, depends if I have money. Si tuviera dinero, compraría un libro = I don't have money, just speculating. English uses tense: 'if I have' vs 'if I had'. Spanish does the same — different tenses.
Never after si — futuro and conditional
Common mistake: Si tendré tiempo (wrong), Si tendría tiempo (wrong). Remember: after si — NEVER futuro, NEVER conditional. Only: present (Type 1) or imperfect subjunctive (Type 2). The main clause, on the other hand, can use either.
Useful templates
Si pudiera, te ayudaría (if I could, I would help you). Si fuera tú, no haría eso (if I were you, I wouldn't do that). Si supieras la verdad… (if you knew the truth…). Si tuviera más tiempo, leería más (if I had more time, I would read more). These structures are B1 gold.
