what is it?
An open conditional sentence expresses a realistic or possible situation: if something happens (or is true), a certain result follows. In Spanish, the condition clause — called the protasis — is introduced by si followed by the present indicative. The result clause — the apodosis — uses the present indicative, the simple future, or an imperative. These sentences describe conditions that the speaker treats as genuinely open: the outcome depends on whether the condition is met.
when to use it
Habitual or general truths. Use it when the result is always or typically true given the condition: Si llueve, me quedo en casa.
Future plans or intentions. Use it when the result is a likely future action: Si terminas pronto, iremos al cine.
Instructions or requests. Use it when the result is a command or suggestion: Si tienes tiempo, llámame.
The two clauses can appear in either order. Si llueve, me quedo en casa and Me quedo en casa si llueve are both correct. When the si clause comes first, it is followed by a comma.
formation
The structure is straightforward. The condition clause always uses si + present indicative. The result clause uses one of three forms:
| si clause (protasis) | result clause (apodosis) | apodosis type |
|---|---|---|
| si + present indicative | present indicative | habitual / general truth |
| si + present indicative | simple future | likely future outcome |
| si + present indicative | imperative | instruction / request |
Below are the present-indicative endings for regular verbs, which are used in the si clause.
| person | -ar (hablar) | -er (comer) | -ir (vivir) |
|---|---|---|---|
| yo | hablo | como | vivo |
| tú | hablas | comes | vives |
| él/ella | habla | come | vive |
| nosotros | hablamos | comemos | vivimos |
| vosotros | habláis | coméis | vivís |
| ellos/ellas | hablan | comen | viven |
examples in context
common pitfalls
Future tense after si. In Spanish, si is never followed by the future tense in the same clause. The condition must use the present indicative.
Incorrect: *Si vendrás mañana, te llamo.
Correct: Si vienes mañana, te llamo.
Missing accent on sí (yes). Without the accent, si is the conjunction «if». With the accent, sí means «yes» or adds emphasis. Dropping the accent changes the meaning entirely.
Incorrect: *Si, claro que voy.
Correct: Sí, claro que voy.
Conditional tense in the apodosis of an open condition. English «if it rains, I would stay» can sound natural in informal speech, but in Spanish a realistic open condition takes the present or future in the result clause — not the conditional. The conditional is reserved for hypothetical or contrary-to-fact situations (a higher-level structure).
Incorrect: *Si llueve, me quedaría en casa.
Correct: Si llueve, me quedo / me quedaré en casa.
Three sentences, graded here. Nothing is saved and no account is needed.
Si no ___ la pistola de agua, no puedes jugar con nosotros. (encontrar)
Fill in the blank with the correct form of the verb in parentheses.