Infinitivo Pessoal com Preposição

Level 4

The Personal Infinitive (Infinitivo Pessoal) is a unique Portuguese feature where the infinitive verb changes its ending to match the subject. It is most commonly used after prepositions like 'para', 'sem', and 'ao' when the subject of the infinitive is different from the main subject.

How It Works

The Infinitivo Pessoal is a nominal form of the verb that allows for subject agreement. While it looks like a tense, it actually functions as a compact alternative to a subordinate clause.

1. Conjugation Pattern:
The endings are added directly to the impersonal infinitive (the dictionary form):

  • Eu: (no ending) — falar
  • Tu: -es — falares
  • Ele/Ela/Você: (no ending) — falar
  • Nós: -mos — falarmos
  • Vós: -des — falardes
  • Eles/Elas/Vocês: -em — falarem

Note on the verb 'pôr': For the verb pôr, the circumflex accent is dropped in all inflected forms (e.g., pormos, porem), remaining only in the 1st and 3rd person singular (pôr).

2. Usage after Prepositions:
This is the most frequent use case. It typically follows prepositions such as para, por, sem, ao, até, or phrases like antes de and depois de.

3. Why use it?
It provides stylistic economy. Instead of saying 'para que eles saibam' (so that they know), which requires the subjunctive, you can say 'para eles saberem'. It is especially useful for clarifying the agent when the subject changes between the main and subordinate clause.

4. Personal Infinitive vs. Future Subjunctive:
For regular verbs, these forms look identical. However, they are triggered differently: the personal infinitive follows a preposition, while the future subjunctive follows a conjunction (like se or quando). Furthermore, irregular verbs use different stems: the personal infinitive uses the infinitive stem (ser → sermos), while the future subjunctive uses the preterite stem (fui → formos).

Examples (5)

  1. Comprei comida para eles comerem.

    I bought food for them to eat.

    Word by Word: I-bought food for them to-eat(they).

    The verb 'comer' takes the '-em' ending because the subject of the eating (them) is different from the subject of the buying (I).

  2. Não saiam sem nós terminarmos o trabalho.

    Don't leave without us finishing the work.

    Word by Word: Not leave(you-plural) without us to-finish(we) the work.

    The preposition 'sem' triggers the personal infinitive 'terminarmos' to show that 'we' are the ones finishing.

  3. Ao entrares na sala, apaga a luz.

    Upon [you] entering the room, turn off the light.

    Word by Word: Upon to-enter(you) in-the room, turn-off the light.

    In European Portuguese, 'ao' + personal infinitive is a very common way to say 'when' or 'upon doing something'.

  4. É melhor vocês saírem agora para não chegarem atrasados.

    It's better for you all to leave now so you don't arrive late.

    Word by Word: Is better you-all to-leave(you-all) now for not to-arrive(you-all) late.

    Both 'saírem' and 'chegarem' are inflected to match 'vocês'.

  5. Apesar de sermos amigos, não concordo contigo.

    Despite us being friends, I don't agree with you.

    Word by Word: Despite of to-be(we) friends, not I-agree with-you.

    Even irregular verbs like 'ser' use the infinitive stem for this form (sermos).

Common Mistakes

  • Using the impersonal (uninflected) infinitive when the subject changes.

    Fiz isto para eles ficar felizes.
    Fiz isto para eles ficarem felizes.

    If the subject of the infinitive (eles) is explicitly mentioned and different from the main subject, you must conjugate the verb (ficarem).

  • Over-inflecting when the subject is the same.

    Nós fomos ao mercado para comprarmos pão.
    Nós fomos ao mercado para comprar pão.

    While not strictly 'wrong', inflecting the infinitive when the subject is the same (Nós... nós) sounds heavy and redundant. The impersonal form is preferred.

  • Confusing irregular stems with the Future Subjunctive.

    Para nós formos felizes, precisamos de paz.
    Para nós sermos felizes, precisamos de paz.

    The personal infinitive always uses the infinitive stem (ser -> sermos). The form 'formos' is the future subjunctive, which is triggered by conjunctions like 'se', not prepositions like 'para'.

How It Connects

Tap a pattern to see what it builds on and what it leads to.

Infinitivo Pessoal com PreposiçãoLevel 4

Learn This First

To use the personal infinitive after a preposition, you must first be able to conjugate the personal infinitive forms and understand that this structure is triggered when the subject of the infinitive clause is different from the main clause subject.