Conditional conjunctions introduce the if behind an action: what has to be true for something else to happen. Spanish has a rich inventory of them, and almost all trigger the subjunctive — with one famous exception, si, which has rules all its own.
Si: if
Si is the ordinary if. Despite being the most common conditional conjunction, it behaves differently from the rest because it can take the indicative in real conditionals. The mood depends on how plausible the condition is.
Real conditions (indicative)
When the condition is simply possible or habitual, use the indicative in the si clause:
Hypothetical conditions (past subjunctive)
When the condition is contrary to fact or purely hypothetical, use the past subjunctive in the si clause and the conditional in the main clause:
Si fueras más puntual, no tendríamos este problema.
If you were more punctual, we wouldn't have this problem.
A menos que: unless
A menos que means unless and always takes the subjunctive.
No iré a la fiesta a menos que tú vayas también.
I won't go to the party unless you go too.
Podemos salir, a menos que estés cansado.
We can go out, unless you're tired.
Salvo que: unless (formal)
Salvo que is a slightly more formal synonym of a menos que, also with the subjunctive.
Saldremos temprano, salvo que haya mal tiempo.
We'll leave early, unless there's bad weather.
Con tal de que: as long as, provided that
Con tal de que introduces a condition the speaker is willing to accept. It takes the subjunctive.
Te presto el carro con tal de que lo cuides.
I'll lend you the car as long as you take care of it.
Siempre y cuando: provided that
Siempre y cuando is a stronger, more explicit provided that, common in contracts, rules, and formal speech.
Puedes quedarte siempre y cuando ayudes con los gastos.
You can stay provided that you help with expenses.
En caso de que: in case
En caso de que introduces a possibility to be prepared for.
Lleva un paraguas en caso de que llueva.
Take an umbrella in case it rains.
Summary: which conjunctions trigger subjunctive?
| Conjunction | Meaning | Mood |
|---|---|---|
| si | if (real) | indicative |
| si | if (hypothetical) | past subjunctive |
| a menos que | unless | subjunctive |
| salvo que | unless (formal) | subjunctive |
| con tal de que | as long as | subjunctive |
| siempre y cuando | provided that | subjunctive |
| en caso de que | in case | subjunctive |
Common mistakes
❌ Si tendría dinero, viajaría.
Wrong: never use the conditional after si — use the imperfect subjunctive.
✅ Si tuviera dinero, viajaría.
Correct: si + imperfect subjunctive, then conditional.
❌ Si llueve mañana, no vayamos.
Wrong: si + present does not take the subjunctive in the result clause.
✅ Si llueve mañana, no vamos.
Correct: si + present indicative, then present indicative or future.
❌ A menos que vienes temprano, no te espero.
Wrong: a menos que always takes the subjunctive.
✅ A menos que vengas temprano, no te espero.
Correct: vengas (subjunctive) after a menos que.
For concessive structures (although, even if), see Concessive: Aunque, A pesar de que. For time clauses that also mix indicative and subjunctive, see Temporal: Cuando, Mientras, Hasta que.
Related Topics
- Temporal: Cuando, Mientras, Hasta queB1 — How to build time clauses in Spanish and choose between indicative and subjunctive after cuando, mientras, hasta que, and friends.
- Concessive: Aunque, A pesar de queB2 — How to express although, even though, and even if with aunque, a pesar de que, and related conjunctions.
- Purpose: Para que, A fin de queB2 — How to express so that and in order that with para que, a fin de que, and related purpose conjunctions, all with the subjunctive.