Future Subjunctive with Temporal Conjunction

This grammar point connects two separate actions. The first action is a trigger in the future. The second action happens because of that trigger. Unlike the "if" (se) clauses, these triggers usually feel certain. You know you will go home eventually. You know your friend will call you. The Future Subjunctive just handles the "when" part. It sits right after words like quando or assim que. It sets the stage for the main verb. The main verb usually stays in the Future or the Imperative. For example, you tell a waiter: "When the food arrives, I will pay." In Portuguese, that "arrives" must be in the Future Subjunctive. It sounds sophisticated but it is very logical once you see it. It is all about pending events that trigger others.

1. 1Start with the 3rd person plural of the Pretérito Perfeito.
2. 2This is the "they" form of the simple past tense.
3. 3For example, for falar, the form is falaram.
4. 4Now, remove the -am ending from that past form.
5. 5You are left with the root: falar-.
6. 6For irregulars like fazer, the form is fizeram, so the root is fizer-.
7. 7For ir or ser, the form is foram, so the root is for-.
8. 8Now, add the specific Future Subjunctive endings to that root.
9. 9The endings are: - (eu), -es (tu), - (você/ele), -mos (nós), -des (vós), -em (vocês/eles).
10. 10Note that the eu and ele forms are exactly the same.
11. 11Regular -ar verbs often look like the infinitive, but do not be fooled.
12. 12Irregular verbs show the true power of this formation rule.

You use this pattern whenever an action depends on a future time. The most common trigger word is quando (when). Use it when ordering food: "Quando a pizza chegar, eu abro a porta." Use it for work deadlines: "Assim que eu terminar o relatório, eu te envio." It is perfect for travel plans too. Use enquanto (while) to show duration in the future. "Enquanto você estiver em Lisboa, visite o Belém." Another great one is logo que (as soon as). It adds a sense of urgency to your plans. Use sempre que (whenever) for repeated future possibilities. "Sempre que você vier a Londres, me avise." These words are your signposts for the subjunctive.

Do not use this for things happening right now. If you are eating, use the Present Indicative. Do not use it for past events either. If the action is a habit, stick to the Indicative. For example: "I always cry quando I vejo this movie." That is a general fact, not a pending future event. If you use the subjunctive there, it sounds like a threat! Also, avoid it after depois de if there is no subject. If you say "After eating," use the infinitive: depois de comer. Only use the subjunctive if you add a "that" (depois que). Many learners over-use it because it feels "fancy." Keep it strictly for future triggers to stay natural.

The biggest mistake is using the Present Indicative by accident. English speakers often say "When I go" using the present. In Portuguese, quando eu vou means "when I usually go." For the future, you must say quando eu for. Another trap is the verb ter. Many say quando eu tenho for the future. The correct form is quando eu tiver. Do not forget that the root comes from the past. If you forget fizer and say fazer, people will understand you. However, you will sound like a textbook from the 1950s. Watch out for the nós form too. It is fizermos, not fazeremos. Finally, do not confuse this with the Personal Infinitive. They look similar but serve very different masters.

Let us look at the Present Subjunctive for a second. That tense is about wishes, doubts, and emotions. The Future Subjunctive is about time and conditions. If you say "I want you to go," use the Present Subjunctive. If you say "When you go," use the Future Subjunctive. Think of the Present Subjunctive as "moody" and the Future as "timely." Also, compare quando with se. Both use the Future Subjunctive. But se implies doubt about the event happening at all. Quando implies the event is certain, just the timing is loose. It is the difference between "If I win the lottery" and "When I get home."