Personal Infinitive in Subject Clauses

Brazilian Portuguese has an elegant, economical sentence type: a personal infinitive that functions as the subject of an impersonal, evaluative clause. É importante nós estudarmos — "It's important that we study," or more literally "For us to study is important." The infinitive clause, complete with its own subject, is the subject of the sentence. This page shows how to build these sentences, why they're so useful, and how they compare to the que + subjunctive clauses they often replace.

For English speakers, this is one of those constructions that feels strange at first and then becomes addictive, because it does so much with so little. Instead of "It is important that we study" (main clause + subordinate clause + subjunctive), Portuguese gives you a single smooth infinitive clause that still tells you exactly who.

The structure

The pattern is: impersonal evaluative expression + (optional subject) + personal infinitive.

The evaluative expression is typically é + adjective or noun: é importante, é difícil, é bom, é melhor, é fundamental, é uma pena, não é justo, vale a pena. The infinitive that follows carries the real subject and inflects to agree with it.

In each, the subject of the sentence is the infinitive clause itself: nós estudarmos, eles entenderem, vocês esperarem. Strip the evaluative part and you can see the infinitive clause is what's being evaluated.

The subject pronoun is often optional

Because the -mos and -em endings already encode the subject, Brazilian Portuguese frequently drops the pronoun when context makes the referent obvious. The inflection alone does the work:

Keep nós when you want to make the subject emphatic or when the discourse hasn't already established who you mean; drop it once "we" is clearly understood. The -mos ending guarantees the meaning either way — this is precisely the economy that makes the personal infinitive so handy.

When there's no expressed subject: the impersonal infinitive

If you make a fully general statement with no particular subject — "one must," "it's important to" — you don't inflect, because there's nobody to agree with. This is the impersonal infinitive (the plain one).

The moment you add a specific subject, the infinitive inflects:

This contrast — impersonal estudar vs. personal estudarmos — is exactly the distinction explored in Personal vs Impersonal Infinitive. The single deciding factor is whether a specific subject is present.

Why this beats que + subjunctive

The same idea can be expressed with a que clause and the subjunctive: É importante que nós estudemos. So why use the infinitive?

Both are correct standard Portuguese. The infinitive version is more economical: it drops the que and replaces the subjunctive's irregular forms (estudemos, entendam, esperem) with the predictable, regular personal infinitive. Because the personal infinitive is built straight on the infinitive, you never have to worry about irregular subjunctive stems — é importante eles virem is far easier to produce than recalling that the subjunctive of vir is venham. This is one of the most economical sentence types in the language, and it's a major reason the personal infinitive is so beloved in Brazil.

The subjunctive version retains a slight edge in formal writing, where the explicit que clause is sometimes preferred, and it can carry a touch more modal weight (a stronger sense of "ought to"). But in speech and most writing, the infinitive is at least as common.

A range of evaluative triggers

These expressions all work the same way with the personal infinitive:

Note the last one: a gente means "we" but is grammatically third-person singular, so the infinitive stays combinar with no ending — not combinarmos. This is a persistent trap and shows up in the mistakes below.

Common Mistakes

Mixing the two structures (keeping que but inflecting the infinitive) is the classic error. Pick one: que + subjunctive, or no que + personal infinitive.

The unifying lesson: when a specific subject is present in one of these evaluative sentences, the infinitive must agree with it — nós → -mos, eles/elas/vocês → -em — and a gente counts as singular.

Key Takeaways

• An impersonal evaluative expression (é importante, é difícil, não é justo, vale a pena) can take a personal infinitive clause as its subject: é importante nós estudarmos.
• The infinitive inflects to agree with its subject; with no specific subject, use the plain infinitive (é importante estudar).
• This construction is a lighter, more regular alternative to que
  • subjunctive (é importante que nós estudemos).
• The subject pronoun can be dropped (é importante estudarmos) because the -mos/-em ending already identifies the subject; keep it for emphasis or clarity.
• A gente takes singular agreement — never -mos.