Condicionales avanzados: a menos que, con tal de que, en caso de que…

Spanish has a tight cluster of conditional conjunctions beyond si — a menos que, a no ser que, con tal de que, siempre que, en caso de que, salvo que, mientras. Each one carves out a specific corner of the conditional space (negative conditions, sufficient conditions, hypothetical contingencies) that si can't reach as elegantly. They all share one feature: they take the subjunctive, every time, no exceptions. This is the load-bearing rule of the whole set.

This page is the B2 follow-up to the core conditional patterns with si. It assumes you already know the three si tense pairings. Here we look at the rest of the conditional toolkit, including mixed conditionals (where the si clause refers to one time and the consequence to another) and the literary patterns de + infinitive and en + gerund.

The subjunctive rule: one rule for the whole set

Every conjunction on this page always triggers the subjunctive in its clause. There is no indicative variant. Memorise that single fact and you've eliminated half the difficulty of the page.

Why? Because each of these conjunctions introduces a condition — a state of affairs that may or may not come about. The action in the conditional clause is not asserted as a fact; it is projected as a contingency. That is the exact territory of the subjunctive (see the indicative/subjunctive logic).

A menos que / a no ser que / salvo que — unless

The negative conditional: unless X happens, Y.... All three are largely interchangeable, with minor register differences. A no ser que is the most colloquial; a menos que the most neutral; salvo que slightly more formal or written. All three take the subjunctive.

A useful observation: unless = if not, and the two often translate to each other. No iré a menos que vengas ≈ no iré si no vienes. The si no version is grammatical but flat; the a menos que version is the more idiomatic and elegant choice in writing or careful speech.

The English-speaker trap: in English, unless is followed by the indicative (unless you come). Spanish requires the subjunctive (a menos que vengas). Forgetting this is one of the most consistent B1/B2 errors.

Con tal de que / siempre que / siempre y cuando — provided that

The positive conditional with a flavour of "the only thing I need is...": I'll do X provided that Y. Con tal de que and siempre y cuando are equivalent and emphatic; siempre que is the most common.

A trap with siempre que: it has two meanings, distinguishable only by mood.

• siempre que + subjunctive = provided that (conditional reading).
• siempre que + indicative = whenever (habitual reading, see temporal conjunctions).

If you want the conditional reading without ambiguity, switch to siempre y cuando or con tal de que.

En caso de que — in case

En caso de que + subjunctive = in case / in the event that. It introduces a precaution against a hypothetical situation.

The related por si (acaso) is a less formal alternative that means roughly the same thing, but it takes the indicative by default in peninsular Spanish — llévate el paraguas por si llueve. With por si, the subjunctive is also possible but less common. En caso de que is unambiguously subjunctive.

Mientras — as long as (conditional)

Mientras has three uses, distinguished by tense:

• mientras + indicative, simultaneity: I read while she cooked — purely temporal.
• mientras + indicative, condition: as long as you study, you'll pass — habitual conditional.
• mientras + subjunctive, condition: as long as you study, you'll pass — future-projected conditional.

The subjunctive mientras is the conditional one closest to English as long as.

The difference between mientras + indicative and mientras + subjunctive in conditional contexts is subtle: indicative reads as a current/habitual condition (as long as you do this — as you generally do); subjunctive reads as a future-projected condition (as long as you do this — going forward). In practice, the subjunctive is the more common conditional choice.

Mixed conditionals — when past and present cross

A high-frequency advanced pattern: the si clause refers to one time period and the consequence to another. The most common combination in everyday speech is past si clause + present/future consequence — if I had studied medicine, I'd be a doctor now.

The pattern: si + pluperfect subjunctive (past condition) → conditional simple (present consequence). Don't expect symmetry — the tense pairing is hybrid by design, because the two clauses are pointing at different times.

The reverse pattern — present condition, past consequence — is less common but possible: si fueras más prudente, no te habrían despedido (if you were more careful, they wouldn't have fired you). Here the personality trait is timeless (imperfect subjunctive fueras), but the consequence is anchored in past time (conditional perfect habrían despedido).

De + infinitive — the literary conditional

A compact, written-register conditional: de + infinitive = if + clause. It functions exactly like a si clause but with no conjugated verb and no si. Used heavily in journalism and formal writing; less common in conversation.

Note the perfect form: de haber + participle maps onto si hubiera + participle — counterfactual past. De + bare infinitive maps onto si + present or si + imperfect subjunctive, with the context disambiguating.

In conversation, this construction sounds bookish. A native speaker would say si tuviera tiempo, iría a verte in normal speech; de tener tiempo belongs in a newspaper editorial or a literary register.

En + gerund — once X-ing

Another compressed conditional/temporal hybrid, characteristically literary: en + gerund = once X happens / as soon as X.

This pattern is firmly literary or archaic in modern Spanish. You'll encounter it in literature and old refrains (el saber no ocupa lugar; en sabiéndolo, mejor). In everyday speech, use en cuanto or cuando + subjunctive instead: en cuanto llegues, llámame.

Cuando + subjunctive — implicit conditional

Although cuando is primarily a temporal conjunction, cuando + subjunctive in a future-projected context can carry a conditional flavour, particularly when paired with a verb of intention or warning.

The distinction between cuando + subjunctive (when) and si + present (if) is real but slippery. Cuando presupposes the event will happen and only timing is uncertain; si leaves open whether it will happen at all. Cuando llegues = when you arrive (you will); si llegas = if you arrive (maybe).

Common Mistakes

Key takeaways

• All the advanced conditional conjunctions take the subjunctive — every time. A menos que, a no ser que, salvo que, con tal de que, siempre y cuando, en caso de que — no indicative variant.
• Siempre que is bi-modal: subjunctive = provided that; indicative = whenever. Use mood to disambiguate.
• Mientras + subjunctive = as long as (conditional, future-projected).
• Mixed conditionals pair a si clause from one time period with a consequence from another. Most common: si + pluperfect subjunctive → conditional simple (si hubiera estudiado, ahora sería).
• De + infinitive is a compact literary equivalent of a si clause. Recognise it in writing; in speech, use si
  • appropriate tense.
• En + gerund is archaic/literary. Stick to en cuanto + subjunctive or cuando + subjunctive in modern speech.
• Por si (acaso) takes the indicative by default in peninsular Spanish; en caso de que always takes the subjunctive.
• The English-speaker trap: every conjunction translatable as unless, provided that, in case, as long as requires the subjunctive in Spanish, regardless of how the English version is built.