1. Si (if) clauses express a condition or event upon which another condition or event depends. Sentences with si clauses are often hypothetical statements. They contain a subordinate clause (si clause) and a main clause (result clause).
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2. The si clause may be the first or second clause in a sentence
The si clause may be the first or second clause in a sentence. Note that a comma is used only when the si clause comes first.
Si tienes tiempo, ven con nosotros.
Iré con ustedes si no trabajo.
If you have time, come with us.
I’ll go with you if I don't work.
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3. Hypothetical statements about the future
In hypothetical statements about conditions or events that are possible or likely to occur, the si clause uses the present indicative. The main clause may use the present indicative, the future indicative, ir a + [infinitive], or a command.
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4. Si salgo temprano del trabajo, voy al cine con Andrés.
Si clause: PRESENT INDICATIVE
Main clause
Si salgo temprano del trabajo,
PRESENT TENSE
voy al cine con Andrés.
If I leave work early,
I’m going to the movies with Andrés.
Si usted no mejora su currículum,
FUTURE TENSE
nunca conseguirá empleo.
If you don’t improve your résumé,
you’ll never get a job.
Si la jefa me pregunta,
IR A + [INFINITIVE]
no le voy a mentir.
If the boss asks me,
I’m not going to lie to her.
Si hay algún problema,
COMMAND
llámenos de inmediato.
If there is a problem,
call us right away.
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6. Hypothetical statements about the present
In hypothetical statements about current conditions or events that are improbable or contrary-to-fact, the si clause uses the past subjunctive. The main clause uses the conditional.
Si clause: PAST SUBJUNCTIVE
Main clause: CONDITIONAL
¡Si ustedes no fueran tan incapaces,
ya lo tendrían listo!
If you weren’t all so incapable,
you’d already have this ready!
Si sacaras un préstamo a largo plazo,
pagarías menos por mes.
If you took out a long-term loan,
you’d pay less each month.
Si no estuviera tan cansada,
saldría a cenar contigo.
If I weren’t so tired,
I’d go out to dinner with you.
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7. A contrary-to-fact situation is one that is possible, but will probably not happen and/or has not occurred.
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9. Habitual conditions and actions in the past
In statements that express habitual past actions that are not contrary-to-fact, both the si clause and the main clause use the imperfect.
Si clause: IMPERFECT
Main clause: IMPERFECT
Si Milena tenía tiempo libre,
siempre iba a la playa.
If Milena had free time,
she would always go to the beach.
Si mi papá salía de viaje de negocios,
siempre me traía un regalito.
If my dad went on a business trip,
he always brought me back a little present.
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