How to Use Portuguese Personal Infinitive in Simple Sentences

Introduction

The infinitivo pessoal is a distinctive feature of Portuguese grammar that often puzzles English-speaking learners. It allows the infinitive to change form according to the subject, adding clarity and flexibility to sentences. This article explains how to use the personal infinitive in simple sentences, with clear rules, step-by-step examples in Brazilian Portuguese, and helpful usage notes.

What is the personal infinitive?

The infinitivo pessoal is a form of the infinitive that varies to agree with different subjects, much like a verb conjugation. In Portuguese, the non-personal infinitive remains unchanged, but the personal infinitive adds endings to show who performs the action. This feature exists in both European and Brazilian Portuguese, though use patterns can differ.

Infinitive forms: impersonal vs personal

There are two main infinitive types:

Impersonal infinitive: the basic form that does not change. Example: falar, comer, partir.

Personal infinitive: the infinitive with endings for subjects. Example: falarmos, comeres, partirem.

Why use the personal infinitive?

The infinitivo pessoal clarifies who is doing the action when the subject is explicit or implied in a clause. It often appears after prepositions, expressions of intention, obligation, or verbs that introduce subordinate clauses. In many cases, it replaces a subordinate clause introduced by que plus a finite verb, offering a more compact and natural sentence structure.

Main situations where the personal infinitive is used

Use the infinitivo pessoal in these common contexts:

1. After prepositions when the subject differs from the main clause subject.

2. After verbs of intention or obligation when the subject is explicit.

3. In adverbial phrases of time, cause, or condition.

4. To avoid a subordinate clause with que when the same subject appears in different clauses.

Forming the personal infinitive

The endings for the infinitivo pessoal are added to the infinitive stem. For regular verbs, the endings depend on the verb group (-ar, -er, -ir) and the subject. The pattern is consistent across groups and is relatively easy to learn.

Personal infinitive endings

Here are the common endings for the personal infinitive (applied to all verb groups):

eu: no ending change when the subject is eu in spoken Brazilian Portuguese; traditional grammar lists endings more for European Portuguese. For clarity in Brazilian usage, the distinct endings are:

tu: -es
ele/ela/você: – (no ending for singular third person, same as impersonal)
nós: -mos
vós: -des (rare in Brazilian Portuguese)
eles/elas/vocês: -em

Examples with falar (to speak):
tu falares
ele falar
nós falarmos
eles falarem

Notes on practical Brazilian usage

In Brazil, the vós form is virtually unused, and speakers often avoid overly formal endings. However, the infinitivo pessoal with nós and eles is common and useful. For many learners, focusing on tu, nós, and eles/vocês forms is sufficient.

Step-by-step: using the personal infinitive in simple sentences

Follow these steps to use the infinitivo pessoal correctly in basic sentences.

Step 1: Identify the clause and its subject

Find the subordinate clause that contains an action after a preposition, verb of intention, or expression. Ask who performs that action. If the subject is different from the main clause subject or explicitly stated, consider using the infinitivo pessoal.

Example:
We want Maria to help us.
In Portuguese: Queremos que Maria nos ajude. Or more naturally: Queremos Maria ajudar nos? Use the personal infinitive to be clear: Queremos que Maria nos ajudar is incorrect; correct: Queremos Maria ajudar-nos or Queremos que Maria nos ajude. Better: Queremos que Maria nos ajude. But in many contexts, you can say: Queremos Maria ajudar a nós? Instead, the personal infinitive is best shown below.

Step 2: Decide if the infinitive needs to reflect the subject

If the subject of the subordinate clause is different or specified, you need the infinitivo pessoal. If the subject is the same as the main clause or unspecified, use the impersonal infinitive.

Same subject example:
Eu quero comer agora. (I want to eat now) — eu is subject of both verbs, use impersonal comer.

Different subject example:
Eu quero tu comeres agora. (I want you to eat now) — different subject tu, use personal infinitive comeres.

Step 3: Apply the correct personal ending

Attach the appropriate ending to the infinitive root depending on the subject. Remember that third person singular looks like the impersonal form, so context or an explicit subject clarifies meaning.

Examples:
Ele pediu para eu falar com ela. (He asked for me to speak with her) — eu is first person, but traditional grammar prefers falar for first person; commonly Brazilians say Ele pediu para eu falar or Ele pediu para eu falar.

More clear with different subject: Ele pediu para Maria falar com ela — Maria is explicit; the infinitive can remain impersonal in appearance but is understood as personal when the subject is stated: Maria falar is interpreted as Maria speaking.

Common structures that use the personal infinitive

The infinitivo pessoal appears in a variety of natural structures. Learn these patterns to recognize and produce sentences easily.

After prepositions

When a preposition introduces an action and the subject differs from the main clause subject, use the personal infinitive.

Example:
Antes de saíres, fecha a porta. (Before you leave, close the door) — saíres agrees with tu.

Example with nós:
Depois de terminarmos, vamos embora. (After we finish, we will leave) — terminarmos matches nós.

After verbs of intention, desire, or obligation

Verbs like querer (to want), mandar (to order), permitir (to allow), and pedir (to ask) commonly use the personal infinitive when the subordinate subject is explicit and different.

Examples:
Quero vocês estudarem mais. (I want you all to study more)
Ela mandou eu esperar fora. (She ordered me to wait outside) — informally you might hear Ela mandou eu esperar fora.

In adverbial phrases (time, condition, cause)

Use the personal infinitive to compress clauses that express time, condition, or cause.

Time example:
Ao chegarmos, avisamos você. (When we arrive, we will notify you) — chegarmos uses nós.

Condition example:
Se eles chegarem cedo, podemos sair juntos. (If they arrive early, we can leave together) — here a finite verb is used, but an alternative: Compras feitas, saímos. For personal infinitive: Com eles chegarem cedo is less natural; prefer se eles chegarem.

Practical examples with translations

Below are clear sentences using the infinitivo pessoal with short English translations for context. Notice how endings change to match each subject.

É importante nós estudarmos todos os dias.
It is important that we study every day.

Peço que tu me ajudes com esse problema.
I ask that you help me with this problem.

Antes de vocês sair, verifiquem as chaves. (common spoken form)
Before you leave, check the keys.

Depois de eles terminarem, podemos conversar.
After they finish, we can talk.

Ela prefere eu ficar em casa hoje.
She prefers that I stay home today.

Para eu entender melhor, explique de novo.
So that I understand better, explain again.

Notes on literal vs natural translations

Some literal English equivalents might sound awkward. Portuguese often uses the infinitivo pessoal where English uses to plus a clause or a finite verb with that. Focus on how Portuguese structures the sentence rather than forcing English logic into it.

Common pitfalls and how to avoid them

Learners make predictable mistakes when using the infinitivo pessoal. Here are the main ones with corrections.

Confusing subject agreement

Mistake: Eu quero tu comer agora.
Correction: Eu quero tu comeres agora.
Remember to change the ending when the subject differs from the main clause subject.

Overusing the impersonal infinitive

Mistake: Antes de nós sair, espere. (sounds wrong)
Correction: Antes de nós saírmos, espere. or Antes de sairmos, espere. Using the personal form clarifies the subject.

Ignoring spoken Brazilian variations

Warning: In spoken Brazilian Portuguese, people often simplify or use constructions that mix forms. For instance, you may hear Eu quero você estudar instead of Eu quero você estudar with a personal ending. These forms are common in colloquial speech, but in formal writing and precise speech, prefer correct personal endings.

Stylistic and cultural notes

Portuguese allows flexibility; Brazilian Portuguese in informal speech tends to be less strict about some personal infinitive forms, especially with first person singular and second person plural forms that are rare in everyday conversation. In formal writing, legal language, and careful speech, use the full personal infinitive forms for clarity and correctness.

Cultural tip: Brazilians often prefer simpler constructions in conversation, using pronouns and context rather than complex verb endings. However, understanding and using the infinitivo pessoal correctly will make your Portuguese sound more accurate and fluent, particularly in written communication, formal speech, and when you want to be unambiguous.

Quick reference: handy patterns

Here are short patterns to remember:

Same subject in both clauses: use impersonal infinitive.
Different subject after preposition or verb of intention: use personal infinitive.

Use personal endings for tu, nós, eles/elas/vocês when the subject is explicit. Vós is rare in Brazil.

Conclusion

The infinitivo pessoal is a powerful tool in Portuguese that helps express who performs an action with precision. By identifying the subordinate clause subject, choosing the appropriate ending, and paying attention to common contexts like prepositions and verbs of intention, you can use the personal infinitive naturally in Brazilian Portuguese. With practice, it will become an intuitive part of your grammar toolbox, improving both clarity and fluency.