Personal Infinitive Errors | Portuguese (Portugal) Grammar

The personal infinitive — infinitivo pessoal — is the feature that most reliably separates fluent from not-yet-fluent Portuguese. It is a finite infinitive: an infinitive that carries person endings. No other major European language has anything quite like it, which means English speakers have no instinct for when to use it, when to skip it, and when to reach for the subjunctive instead. The errors cluster around a small number of patterns, and once you see them clearly the whole construction clicks into place. This page catalogues every mistake English speakers make with the personal infinitive in European Portuguese and shows you exactly how to correct each one.

A five-second refresher on the forms

Before we look at errors, make sure you can produce the endings without hesitation. The personal infinitive is regular for every verb in the language, including verbs that are irregular in every other tense.

Subject	falar	comer	partir	ser
eu	falar	comer	partir	ser
tu	falares	comeres	partires	seres
ele / ela / você	falar	comer	partir	ser
nós	falarmos	comermos	partirmos	sermos
vós	falardes	comerdes	partirdes	serdes
eles / elas / vocês	falarem	comerem	partirem	serem

The endings are simply -, -es, -, -mos, -des, -em attached to the full infinitive. Notice that eu and the ele forms look identical to the plain infinitive — this is why learners sometimes fail to recognize the personal infinitive when it appears.

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The personal infinitive is completely regular. Even notorious irregulars like ser, ter, vir, pôr and fazer follow the pattern exactly: sermos, termos, virmos, pormos, fazermos. If you find yourself wanting to irregularize one of these, stop — you are reaching for the subjunctive by mistake.

Mistake 1: Missing inflection when the subject is overt

The most common error is using the plain infinitive where European Portuguese demands an inflected one. Whenever the infinitive has a subject that is different from the main clause — or is explicitly stated — and the construction takes a preposition or an impersonal expression, PT-PT inflects.

❌ É bom eles chegar cedo.

Incorrect — a third-person plural subject with an infinitive demands inflection.

✅ É bom eles chegarem cedo.

It's good that they arrive early.

❌ Para nós sair juntos, preciso de sair mais cedo do trabalho.

Incorrect — *nós* requires *-mos*.

✅ Para nós sairmos juntos, preciso de sair mais cedo do trabalho.

For us to leave together, I need to finish work earlier.

Leaving the infinitive uninflected here is the single clearest marker that a learner has not yet internalized European Portuguese syntax. Brazilians can often get away with the plain infinitive in these contexts; in Portugal, the sentence sounds unfinished.

Mistake 2: Over-inflecting with a same-subject verb

The flipside is reaching for the personal infinitive when the subject is the same as the main verb. If one person is doing both actions, European Portuguese uses the plain infinitive — no inflection, no clause.

❌ Eles querem chegarem cedo.

Incorrect — same subject, so no inflection.

✅ Eles querem chegar cedo.

They want to arrive early.

❌ Nós tentamos comermos menos açúcar.

Incorrect — one subject for both verbs.

✅ Nós tentamos comer menos açúcar.

We're trying to eat less sugar.

The logic is clean: if the subject carries over from the main clause, there is nothing to distinguish — Portuguese has no reason to mark the same subject twice. Verbs of volition (querer, desejar, preferir), modal-like verbs (poder, saber, tentar), and aspectual verbs (começar a, acabar de, continuar a) all behave this way when the subject doesn't change.

Mistake 3: Using the infinitive when the subjunctive is required

This is the mirror-image mistake, and it happens when learners discover the personal infinitive and start using it everywhere. After a subordinator like que, antes que, embora, a fim de que, caso — any conjunction that introduces a full subordinate clause — you need the subjunctive, not the infinitive.

❌ Quero que chegarem cedo.

Incorrect — *que* introduces a subjunctive clause, not an infinitive.

✅ Quero que cheguem cedo.

I want them to arrive early.

❌ Embora estudarem muito, não passaram no exame.

Incorrect — *embora* demands the subjunctive.

✅ Embora estudem muito, não passaram no exame.

Even though they study hard, they didn't pass the exam.

The test is mechanical: if the word before the verb is que (or a que-containing conjunction), you need a conjugated verb in the subjunctive. No que, no subjunctive.

Mistake 4: Confusing antes que with antes de

A whole set of conjunctions has a que-form that takes the subjunctive and a de-form that takes the personal infinitive. Both are correct Portuguese, but they are not interchangeable in register or rhythm. Learners often blend them.

Antes que eles cheguem, vamos pôr a mesa.

Before they arrive, let's set the table. (subjunctive — formal, slightly more written)

Antes de eles chegarem, vamos pôr a mesa.

Before they arrive, let's set the table. (personal infinitive — lighter, more common in speech)

❌ Antes eles chegarem, vamos pôr a mesa.

Incorrect — *antes* alone is not a conjunction; you need either *antes que* or *antes de*.

Sem que nos digam nada, já sabemos o resultado.

Without them saying anything, we already know the result. (subjunctive)

Sem nos dizerem nada, já sabemos o resultado.

Without them saying anything, we already know the result. (personal infinitive)

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The de-form with the personal infinitive is generally lighter, shorter, and more common in everyday European Portuguese. The que-form with the subjunctive is a touch more formal and appears more often in writing. Both are fully correct.

Mistake 5: Wrong endings

The endings themselves are simple, but English speakers often miss the distinction between -es (for tu) and -em (for eles), and occasionally borrow subjunctive endings by accident.

✅ Para tu saberes a resposta, tens de estudar.

For you to know the answer, you have to study. (*tu* takes *-es* — correctly inflected.)

Here is the common misstep:

❌ É importante tu saber isso.

Incorrect for PT-PT — *tu* demands *saberes*.

✅ É importante tu saberes isso.

It's important that you know this.

❌ Para eles falar, precisam de silêncio.

Incorrect — *eles* takes *-em*: *falarem*.

✅ Para eles falarem, precisam de silêncio.

For them to speak, they need quiet.

The vós form (-des) is archaic in modern European Portuguese outside the north of the country and a few religious contexts. Don't use it in ordinary speech; you will sound like you stepped out of a seventeenth-century play.

Mistake 6: Treating irregular verbs as irregular

Because ser, ter, fazer, pôr and vir are wildly irregular in tenses like the preterite and subjunctive, learners sometimes try to be clever and irregularize them in the personal infinitive. Don't.

❌ Para nós formos à festa, temos de arranjar um carro.

Incorrect — *ir* is fully regular in the personal infinitive: *irmos*, not *formos*. (*Formos* is the future subjunctive of *ser*, not a personal infinitive of *ir*.)

✅ Para nós irmos à festa, temos de arranjar um carro.

For us to go to the party, we have to get a car.

✅ É importante eles serem pontuais.

It's important that they be punctual. (*serem* looks strange next to the bewildering paradigm of *ser*, but that is exactly the form you need. Regular. Every time.)

Mistake 7: Forgetting inflection after a, de, para, sem, ao

After the common prepositions a, de, para, sem, por and the contraction ao, European Portuguese inflects the infinitive whenever the subject is different from the main clause — or is named explicitly. This is where PT-PT diverges most sharply from Brazilian Portuguese, and where English speakers most often sound unnatural.

✅ Ao saíres de casa, fecha a porta.

When you leave the house, close the door.

✅ Sem estudarmos, não vamos passar no exame.

Without studying, we're not going to pass the exam.

✅ Depois de eles acabarem o trabalho, vamos jantar.

After they finish the work, we'll have dinner.

✅ Para eu chegar a horas, tenho de sair já.

For me to arrive on time, I have to leave now. (*Eu* and *ele* forms have no ending, so the inflected and plain infinitives look identical here — this is why learners often don't notice the personal infinitive at all for singular subjects.)

✅ Para chegarmos a horas, temos de sair já.

For us to arrive on time, we have to leave now. (The *-mos* ending makes the inflection visible.)

Mistake 8: Over-inflecting with a single-subject impersonal

When the impersonal construction genuinely has no subject — or only an understood generic subject — the plain infinitive is correct. Adding an ending is wrong.

❌ É proibido fumarem aqui.

Ambiguous at best. If there is no specific group, use the plain infinitive.

✅ É proibido fumar aqui.

Smoking is forbidden here.

✅ É proibido vocês fumarem aqui.

It is forbidden for you (all) to smoke here.

The difference is whether the sentence has a specific subject for the infinitive. É proibido fumar is a general prohibition addressed to no one in particular. É proibido vocês fumarem names the group. Both are correct; they simply mean different things.

Mistake 9: Dropping inflection in coordinated infinitives

In careful European Portuguese, coordinated infinitives that share a subject both inflect. Colloquial speech sometimes drops the inflection on the second verb — this is tolerated but flagged in formal writing.

✅ Para chegarmos cedo e comermos com calma, temos de sair já.

For us to arrive early and eat without rushing, we have to leave now. (formal)

Para chegarmos cedo e comer com calma, temos de sair já.

Same meaning, colloquial — second infinitive uninflected. Avoid in writing.

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In formal and written European Portuguese, inflect every coordinated infinitive. In everyday speech, native speakers sometimes drop the second one, but imitating this shortcut before you have the basic pattern down will confuse your listeners.

Mistake 10: Using the Brazilian default in Portugal

European Portuguese uses the personal infinitive far more robustly than Brazilian Portuguese does. Brazilians frequently reach for a que-clause with the indicative or simply leave the infinitive uninflected; in Portugal this sounds either foreign or Brazilian-influenced.

Brazilian pattern: É importante nós chegar cedo.

Acceptable in casual Brazilian speech, unidiomatic in Portugal.

✅ PT-PT: É importante nós chegarmos cedo.

It's important for us to arrive early.

If your Portuguese teachers are Brazilian or your exposure is largely to Brazilian content, your instincts here will be wrong. Force yourself to inflect whenever the subject is overt or different from the main clause.

Decision flowchart

When you want to link two verbs in European Portuguese, run through these three questions in order:

Is the subject of the second verb the same as the first? → Plain infinitive. Ela quer sair.
Is the second verb introduced by que (or embora, caso, para que, antes que, a fim de que)? → Subjunctive. Ela quer que eu saia.
Is the second verb introduced by a preposition (a, de, para, sem, por, ao) and does it have its own subject? → Personal infinitive. Para ela sair, preciso de…

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The fast test: if you can put que in front without adding a preposition, you probably need the subjunctive. If there is already a preposition, you probably need the personal infinitive.

Common Mistakes: quick reference

❌ É bom eles chegar cedo.

Missing inflection with overt subject.

✅ É bom eles chegarem cedo.

Correct — *-em* for *eles*.

❌ Eles querem chegarem cedo.

Over-inflecting with same subject.

✅ Eles querem chegar cedo.

Same subject — plain infinitive.

❌ Quero que chegarem cedo.

Infinitive where subjunctive is needed.

✅ Quero que cheguem cedo.

After *que*, use the subjunctive.

❌ Para nós formos lá.

Irregularizing a regular paradigm.

✅ Para nós irmos lá.

The personal infinitive is always regular.

❌ Depois de eles chegar, falamos.

PT-PT demands inflection with an overt subject.

✅ Depois de eles chegarem, falamos.

After they arrive, we'll talk.

Master these five correction pairs and you will have eliminated eighty per cent of the personal-infinitive errors you still make. Everything else is refinement.

Key takeaways

The personal infinitive is always regular, for every verb in the language.
Use it when the subject of the infinitive is different from the main verb's subject — or when the subject is named explicitly even if it matches.
Use it after prepositions (a, de, para, sem, por, ao) when the infinitive carries its own subject.
Use the plain infinitive when both verbs share the same subject and no conjunction intervenes.
Use the subjunctive whenever que (or a que-conjunction) introduces the subordinate verb.
In European Portuguese, inflect more aggressively than in Brazilian Portuguese; under-inflection is the single loudest learner marker.