Conditions beyond si: siempre que, en caso de que, a no ser que, de no ser por

Si is the all-purpose "if" (Hypotheses: si tuviera, iría). Spanish also has a set of conditional connectors that say what kind of condition you mean: a requirement, a possibility you are preparing for, an exception, or the one thing that made the difference. Most of them take the subjunctive, because the condition is not yet a fact. You met some of them in para que, antes de que, sin que, a menos que, con tal de que; this lesson adds the contrasts.

Requirement: siempre que, siempre y cuando

With the subjunctive, siempre que means "provided that". Siempre y cuando is the same, slightly more insistent, and common in negotiation and contracts.

• Te acompaño siempre que no volvamos muy tarde.I'll come with you provided we don't get back too late.
• Firmaremos siempre y cuando se respeten los plazos.We'll sign as long as the deadlines are met.

With the indicative, siempre que is not a condition at all: it means "whenever", for a repeated situation.

• Siempre que voy a Bilbao, como en el mismo restaurante.Whenever I go to Bilbao, I eat at the same restaurant.

Possibility you prepare for: en caso de que, por si

En caso de que + subjunctive = "if, in the event that". Before a noun or an infinitive, drop que: en caso de avería, en caso de duda.

• En caso de que no puedas venir, avísame con tiempo.If you can't come, let me know in good time.
• En caso de avería, llame al número que aparece en la factura.In the event of a breakdown, call the number on the invoice.

Por si = "just in case". It takes the indicative (or, less often, the imperfect subjunctive: por si lloviera), never the present subjunctive.

• Llévate dinero por si no aceptan tarjeta.Take some cash in case they don't take cards.

Exception: a no ser que, a menos que, salvo que

All three mean "unless" and take the subjunctive. Salvo que and excepto que sound more formal and are typical of contracts and rules.

• El partido se jugará a no ser que llueva mucho.The match will be played unless it rains heavily.
• No te llamaré a menos que sea urgente.I won't call you unless it's urgent.
• Salvo que se indique lo contrario, los precios incluyen el IVA.Unless otherwise stated, prices include VAT.

The deciding factor: de no ser por

De no ser por + noun = "if it weren't for, if it hadn't been for". For a clearly past situation you can also say de no haber sido por.

• De no ser por mi hermana, nunca habría estudiado Medicina.If it hadn't been for my sister, I'd never have studied medicine.
• De no haber sido por el GPS, nos habríamos perdido.If it hadn't been for the GPS, we'd have got lost.

Threat or warning: como + subjunctive

In conversation, como + subjunctive is a condition that sounds like a warning. With the indicative, como at the start of a sentence means "since" (cause).

• Como no me devuelvas el libro, no te presto nada más.If you don't give me the book back, I'm not lending you anything else.

Tense in the past

After a past main verb, the subjunctive moves to the imperfect (Which subjunctive? Sequence of tenses): Aceptó siempre que le pagaran el viaje.

Latin America

The connectors are the same across the Spanish-speaking world. A menos que and a no ser que are both common everywhere, and in Latin America the past forms appear mostly with -ra (le pagaran).

Common mistakes

• En caso de que llueve: en caso de que needs the subjunctive, en caso de que llueva.
• Por si llueva: por si never takes the present subjunctive; say por si llueve.
• Reading siempre que + indicative as "provided that": Siempre que viene, discutimos means "whenever he comes".
• A no ser por tu ayuda for "if it weren't for your help": that is de no ser por tu ayuda. A no ser que introduces a clause.
• Using threatening como in a formal text: in a contract or a polite email, use si or salvo que.