what is it?
Spanish has a set of conditional connectors that go beyond the basic si + indicative/subjunctive pattern. Each connector encodes a specific logical relationship — precaution, stipulation, exception, or exclusion — and each one governs a fixed mood in the subordinate clause. Choosing the wrong mood is not a stylistic slip; it produces an ungrammatical or semantically different sentence.
when to use it
por si (acaso) + indicative — expresses a precautionary motive: the speaker acts in advance because something might happen. The subordinate clause states the contingency as a real, open possibility, hence the indicative. The imperfect subjunctive is also possible for a more remote or hypothetical tone, but the present subjunctive is never used here.
siempre que / siempre y cuando / con tal de que / a condición de que + subjunctive — express a stipulation or condition that must be met for the main clause to hold. Because the condition refers to a future or hypothetical event that has not yet been verified, the subjunctive is obligatory.
salvo si / excepto si + indicative — introduce an exception to the main clause, functioning like a plain if-clause. The indicative is used because the exception is framed as a factual scenario, not a hypothetical one.
a no ser que / salvo que + subjunctive — mean «unless» and negate the condition. Because they introduce a hypothetical exception that would block the main clause, the subjunctive is required.
formation
The table below summarises each connector, the mood it requires, and its core meaning.
| connector | mood of subordinate verb | core meaning |
|---|---|---|
| por si (acaso) | indicative (or imperfect subjunctive) | in case |
| siempre que | subjunctive | provided that / as long as |
| siempre y cuando | subjunctive | provided that / as long as |
| con tal de que | subjunctive | provided that / as long as |
| a condición de que | subjunctive | on condition that |
| salvo si / excepto si | indicative | except if |
| salvo que | subjunctive | unless |
| a no ser que | subjunctive | unless |
The main clause itself is not restricted to any particular tense: you can combine these connectors with a present, future, conditional, or imperative in the main clause depending on context.
Note the contrast between salvo si (indicative, «except if») and salvo que (subjunctive, «unless»). The two connectors look similar but belong to different mood categories and carry subtly different meanings.
examples in context
common pitfalls
Present subjunctive after por si (acaso). This connector takes the indicative (or, for a more remote contingency, the imperfect subjunctive). The present subjunctive is not permitted.
✗ Llévate el paraguas por si acaso llueva. ✓ Llévate el paraguas por si acaso llueve.
Indicative after con tal de que / siempre y cuando. These stipulation connectors always require the subjunctive. Using the indicative is a direct error, not a register choice.
✗ Iré con tal de que tú también vienes. ✓ Iré con tal de que tú también vayas.
Confusing salvo si (indicative) with salvo que (subjunctive). The two connectors are not interchangeable. Salvo si introduces a factual exception and takes the indicative; salvo que means «unless» and takes the subjunctive. Mixing their moods produces an error.
✗ Saldremos, salvo si haya un imprevisto. ✓ Saldremos, salvo si hay un imprevisto. / Saldremos, salvo que haya un imprevisto.
Three sentences, graded here. Nothing is saved and no account is needed.
¡Como ___ a perder el vuelo por llegar tarde al aeropuerto, te quedas sin vacaciones este verano! (volver)
Fill in the blank with the correct form of the verb in parentheses.