what is it?
An adverbial clause modifies the main verb by expressing time, purpose, or condition. In Spanish, certain conjunctions that introduce these clauses — notably cuando (when), antes de que (before), después de que (after), and para que (so that / in order that) — require the subjunctive mood in the subordinate clause. The subjunctive is triggered either because the event is projected into an unrealised future, or because the clause expresses purpose rather than fact.
when to use it
cuando + future reference. When «cuando» introduces a clause that refers to a future or hypothetical event, the verb in that clause must be in the present subjunctive, not the future indicative. This applies whenever the main clause is in the future, a command, or any other forward-looking form.
antes de que — always subjunctive. Because «antes de que» refers to an event that has not yet happened at the time described, it invariably takes the subjunctive. There is no indicative alternative with this conjunction.
después de que + subjunctive (future reference). Like «cuando», «después de que» takes the subjunctive when the event it introduces has not yet occurred. When referring to a completed past event, it takes the indicative instead.
para que — always subjunctive. «Para que» expresses purpose and requires the subjunctive whenever the subject of the purpose clause is different from the subject of the main clause. If both clauses share the same subject, use «para» + infinitive instead.
formation
The present subjunctive is formed by taking the first-person singular present indicative, dropping the -o, and adding the «opposite vowel» endings: -ar verbs take -e- endings; -er/-ir verbs take -a- endings. The table below shows the three verbs most relevant to this topic.
| person | llegar (to arrive) | entender (to understand) | salir (to leave) |
|---|---|---|---|
| yo | llegue | entienda | salga |
| tú | llegues | entiendas | salgas |
| él/ella/usted | llegue | entienda | salga |
| nosotros | lleguemos | entendamos | salgamos |
| vosotros | lleguéis | entendáis | salgáis |
| ellos/ustedes | lleguen | entiendan | salgan |
Note the spelling change in «llegar»: the g becomes gu before e to preserve the hard /g/ sound (llegu-). This is a purely orthographic adjustment, not an irregular conjugation.
examples in context
common pitfalls
Future indicative after «cuando». A common error is «*cuando llegaré» by analogy with English «when I will arrive». Spanish does not use the future indicative in these temporal clauses; use the present subjunctive: «cuando llegue».
Indicative after «antes de que». Unlike «después de que», which can take the indicative for past events, «antes de que» has no indicative use at all. Writing «*antes de que llega» is always wrong; the correct form is «antes de que llegue».
«para» + infinitive vs. «para que» + subjunctive. When both clauses share the same subject, use «para» + infinitive: «estudio para aprender» (I study to learn). When the subjects differ, «para» + infinitive is ungrammatical — you must use «para que» + subjunctive: «te lo explico para que lo entiendas», not «*te lo explico para entender».
Three sentences, graded here. Nothing is saved and no account is needed.
El libro está escrito con letra muy pequeña; te compraré unas gafas para que lo ___ más fácilmente. (leer)
Fill in the blank with the correct form of the verb in parentheses.