Real conditions: si + present

What it is

A real condition (oración condicional real) talks about something that can actually happen: if it rains, if you have time, if the flight leaves on time. It has two parts: the condition, introduced by si (if), and the result. English grammars call this the "first conditional".

Si llueve, nos quedamos en casa. (If it rains, we’ll stay at home.)

Spanish uses the present indicative (presente de indicativo) after si, even when the condition is about the future. English works the same way ("if it rains tomorrow", not "if it will rain"), so the pattern feels familiar. The result is where you choose the tense.

How to form it

The condition is always si + present indicative. The result depends on what you want to do:

Word order is free. When the si clause comes first, put a comma after it; when the result comes first, no comma:

• Si tienes tiempo, llámame.If you have time, call me.condition first: comma
• Llámame si tienes tiempo.Call me if you have time.result first: no comma
• Te presto mi bicicleta si me la devuelves el domingo.I’ll lend you my bike if you give it back to me on Sunday.pronouns work as usual

To make the condition negative, put no straight after si: Si no te apuras, vamos a perder el autobús.

When to use it

Offers and suggestions. With the present in both halves, the sentence sounds friendly and spontaneous: Si quieres, te acompaño al médico. Si te parece bien, nos vemos a las ocho.

Instructions and requests, with the imperative: Si Diego llama, dile que estoy en una reunión. Si tienes dudas, escríbeme.

Predictions and plans, with the future or ir a. Spoken Latin American Spanish prefers ir a: Si hace buen tiempo el domingo, vamos a ir a la playa. The future sounds more formal: Si el vuelo sale a tiempo, llegaremos a Lima a las seis. The present works too, especially for things already arranged or decided: Si el vuelo sale a tiempo, llegamos a las seis.

General truths and habits. Here si is close to cuando (whenever): Si mezclas azul y amarillo, sale verde. Si como tarde, duermo mal.

Advice. The conditional of advice (deberías, podrías) also fits in the result: Si te duele la cabeza, deberías descansar un rato.

Things that may already have happened. When you don’t know what happened, si also takes past tenses: Si ya terminaste, ayúdame con la cena.

Contrasts and traps

• No future after si: Si llueve mañana…, never si lloverá. The future can go in the result: nos quedaremos.
• No subjunctive after si: si puedes, si tienes, never si puedas or si tengas.
• si or sí? si = if; sí = yes. Si tienes tiempo, llámame · Sí, tengo tiempo.
• si no or sino? "If not" is two words: Si no puedes venir, avísame. Sino is a different word ("but rather").
• Real or imagined? Si tengo dinero, me compraré un carro (it may happen). For situations you only imagine, Spanish uses si + imperfect subjunctive + conditional: Si tuviera dinero, me compraría un carro (B2 preview). Don’t mix the two: si tengo… compraría is wrong.
• si or cuando? For habits they are close: Si llueve, me quedo en casa ≈ Cuando llueve, me quedo en casa. For a single future event, si leaves the door open: Si llueve mañana… (maybe it won’t).
• si meaning "whether": after saber or preguntar, si introduces a question, not a condition, and the future is fine there: No sé si vendrá (I don’t know whether she’ll come).

If you also speak Portuguese

Portuguese uses the future subjunctive after se (se chover, se você puder); Spanish uses the plain present indicative: si llueve, si puedes. Watch out for regular verbs, where the Portuguese form looks like an infinitive: se você chegar → si llegas, never si llegar. And don’t swap in a Spanish subjunctive either: si puedas is wrong.