Future subjunctive in Portuguese: user manual

“When I go,” “if they do”… These forms are intriguing at first. Portuguese has a subjunctive in the future to talk about an event that is still hypothetical or conditional in the future. Good news: the formation is regular in the vast majority of cases.

The rule in clear terms

The future subjunctive (conjuntivo futuro) is used after conjunctions that point to an uncertain future: if, when, while, as soon as, as soon as, after, where, who, etc. Example: “When I arrive, I’ll call.” (= Quand j’arriverai, j’appelle.) In a real future condition: “If they come, the meeting starts.” The reference grammar precisely describes this usage after “if” and “when” for the value of future possibilityaccording to Ciberdúvidas.

To form the tense, start from the 3rd person plural of the pretérito perfeito (simple past/“passé composé” in Portuguese), remove the ending -am, then add the following endings, which are the same for all verbs: nothing / -es / nothing / -mos / -des / -em. In other words: eu radical], tu radical]es, ele/ela/você radical], nós radical]mos, vós radical]des, eles/elas/vocês radical]em. Irregular verbs follow the same logic from their 3rd person plural: “fizeram” → “fizer-”; “estiveram” → “estiver-”. You can check the tables in a good conjugation dictionarylike Priberam.

Traps and nuances

1. Personal infinitive vs future subjunctive.The forms often look alike ("cantar", "cantarmos", "cantarem"). Golden rule: after a preposition (para, sem, antes de, depois de, por, ao…), use the personal infinitive. Example: “After we arrive, we will have dinner.” But with a conjunction, we use the future subjunctive: “After I arrive, we will have dinner.”
2. Future conditionals. With “if” for a realistic future condition, use the future subjunctive in the protasis, and the simple future (or imperative) in the apodosis: “If you come, I will let you know.” / “If they come, come in.” Avoid the conditional in the apodosis for a real future condition.
3. Brazil vs Portugal. In Brazil, “você” takes the 3rd person: “If you do…”. In Portugal, the informal “tu” remains common, so “If you do…”. In informal spoken language, you sometimes hear other solutions, but the careful norm recommendsstill the future subjunctive after “if”/“when” for an uncertain futureaccording to Ciberdúvidas.
4. Very irregular verbs. Keep in mind the roots from the plural perfect preterite: “for-” (ir/ser), “vier-” (vir: “vierem”), “trouxer-” (trazer: “trouxerem”), “puser-” (pôr: “puserem”), “disser-” (dizer: “disserem”). A glance at a reliable table likePriberam helps to anchor these families.

My experience

At first, I confused the personal infinitive and the future subjunctive: “after we arrive” vs “after I arrive.” The breakthrough came when I imagined atimeline. If I see aprepositionBefore the verb, I switch to the personal infinitive. If I hear a conjunction that triggers a future scenario (if/when/while/as soon as…), I go to the future subjunctive. Since then, my sentences like "When I go to Lisbon, I will visit…" come out more naturally.

How to practice

Create templates: "If I [verb], I will…", "When they [verb], we…", and fill in with 3-4 irregular verbs (to go, to come, to put, to do). You can work on the endings in the Conjugation module of Discus — useful for targeting tenses — and randomly alternate persons: try "if I go", "if we go", "if they go".

To learn more about the language itself, also take a look at the Portuguese page of Discus: /fr/langues/portuguese.

To go further

From a syntactic perspective, the future subjunctive appears in the protasis of potential conditionals ("If you come…") and in temporal subordinate clauses./concessivesreferring to an unrealized later moment ("While we are...", "As soon as they do..."). Morphologically, its paradigm is isomorphic to that of thepersonal infinitive (zero, -es, zero, -mos, -des, -em), hence the frequent homophonies; it is thegoverning (preposition vs conjunction) that separates the two systems in use. In diatopic variation, the preference for "tu" (PT) or "você" (BR) does not affect the mood, but only the inflected person: "tu fizeres" ~ "você fizer". Verbs with an elongated radical theme in the pretérito perfeito (e.g. "fizeram", "trouxeram", "puseram") project this radical into the future subjunctive ("fizer-", "trouxer-", "puser-"), which explains the apparent irregularity without creating formation exceptions. For nomenclature and complete paradigms, see the conjugation tables ofPriberam and the explanatory notes fromCiberdúvidas.