ao + Personal Infinitive

Upon Doing with Personal Infinitive

Level 3

The construction ao + infinitivo pessoal creates a temporal clause meaning 'upon [doing]' or 'when [doing]'. It is a more elegant and concise alternative to using quando (when).

How It Works

The ao + infinitivo pessoal construction is a hallmark of Portuguese syntax used to express actions that happen simultaneously or immediately after one another, often translated as "upon doing" or "when doing."

1. Formation:
It consists of the preposition a + the masculine article o (forming ao), followed by the personal infinitive. The personal infinitive is formed by adding these endings to the dictionary form of the verb:

  • Eu: (no ending)
  • Tu: -es
  • Ele/Ela/Você: (no ending)
  • Nós: -mos
  • Vós: -des
  • Eles/Elas/Vocês: -em

2. Usage and Word Order:
The primary advantage of this construction is clarity. Because the infinitive is inflected for person, you can have a different subject in the temporal clause than in the main clause. A distinct syntactic feature is that the subject often follows the verb: Ao chegarem os convidados, a festa começou (Upon the guests arriving, the party started).

3. Register and Distinctions:
In European Portuguese, this construction frequently replaces the temporal or adverbial gerund (e.g., "Upon arriving"). Note that it is distinct from the progressive construction (e.g., "I am eating"), which uses estar a + infinitivo without the article o.

4. Versatility with Prepositions:
While common with ao, the personal infinitive is also used with many other prepositions to indicate different relationships, such as para (purpose), sem (without), depois de (after), and antes de (before).

5. Regularity:
A key benefit for learners is that the personal infinitive is perfectly regular for every verb in Portuguese, including irregulars like ser (ao sermos) or ir (ao irem).

Examples (4)

  1. Ao entrarmos na sala, todos se calaram.

    Upon our entering the room, everyone went silent.

    Word by Word: To-the enter-we in-the room, all themselves silenced.

    The verb 'entrar' takes the '-mos' ending to show that 'we' (nós) are the ones entering.

  2. Ao verem o acidente, as pessoas chamaram a ambulância.

    When they saw the accident, the people called the ambulance.

    Word by Word: To-the see-they the accident, the people called the ambulance.

    The ending '-em' on 'ver' matches the plural subject 'as pessoas'.

  3. Ao chegares a casa, liga-me.

    When you get home, call me.

    Word by Word: To-the arrive-you to home, call-me.

    The '-es' ending indicates the subject is 'tu' (informal you).

  4. Ao ouvirem a notícia, eles ficaram tristes.

    Upon hearing the news, they became sad.

    Word by Word: To-the hear-they the news, they stayed sad.

    Even though the subject 'eles' is in the main clause, the personal infinitive 'ouvirem' reinforces who heard the news.

Common Mistakes

  • Using the future subjunctive stem for irregular verbs.

    Ao formos amigos, tudo era fácil.
    Ao sermos amigos, tudo era fácil.

    The personal infinitive always uses the dictionary form (ser) as its base, never the subjunctive stem (for-).

  • Forgetting to inflect the verb for plural subjects.

    Ao chegar os convidados, servimos o jantar.
    Ao chegarem os convidados, servimos o jantar.

    When the subject of the 'ao' clause is plural (os convidados), the verb must take the '-em' ending for clarity.

  • Adding 'que' after 'ao'.

    Ao que sairmos, fechamos a porta.
    Ao sairmos, fechamos a porta.

    The contraction 'ao' connects directly to the infinitive; adding 'que' is ungrammatical in this construction.

How It Connects

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

ao + Personal InfinitiveLevel 3Upon Doing with Personal Infinitive

Learn This First

To understand 'ao + infinitivo pessoal', you first need to be familiar with the contraction 'ao' (meaning 'at the' or 'upon') and how to conjugate the personal infinitive, as this pattern uses those specific forms to indicate a simultaneous action with a clear subject.

Learn Next

Patterns that build on this one.

Words in This Pattern