An infinitive clause packs a whole subordinate idea into an infinitive instead of a full conjugated verb. Where English would say "before I left" or "so that they would come," Portuguese can often say antes de sair or para eles virem — shorter, smoother, and frequently preferred. The remarkable tool that makes this possible is the personal infinitive, a Portuguese feature with no real equivalent in English or even in the other major Romance languages.
Why infinitive clauses exist
A finite subordinate clause needs a conjunction (que, quando, para que) and a fully conjugated verb. An infinitive clause replaces both with a single non-finite verb form. The payoff is economy: fewer words, no mood juggling, and a cleaner sentence.
Antes de sair, apaguei todas as luzes.
Before leaving, I turned off all the lights.
Compare the heavier finite version — Antes de que eu saísse... — which Portuguese speakers almost never use when the subject is obvious. The infinitive does the job in half the words.
The impersonal infinitive after prepositions
When the subject of the infinitive is clear from context (usually the same as the main clause), Portuguese uses the plain impersonal infinitive — the bare dictionary form — after a preposition. This is the most common and most beginner-friendly type of infinitive clause.
| Preposition + infinitive | Meaning |
|---|---|
| antes de sair | before leaving |
| depois de comer | after eating |
| sem pensar | without thinking |
| além de estudar | besides studying |
| por ter chegado | for having arrived |
Depois de comer, a gente foi dar uma volta.
After eating, we went for a walk.
Ele saiu sem pensar nas consequências.
He left without thinking about the consequences.
Fui multado por ter estacionado no lugar errado.
I got fined for having parked in the wrong place.
The personal infinitive — when the clause keeps its own subject
Here is what makes Portuguese special. The infinitive can be inflected for person, which lets a subordinate clause carry its own explicit subject without becoming a finite que-clause. The endings attach to the infinitive:
| Person | Ending | Example (fazer) |
|---|---|---|
| eu | — (no ending) | fazer |
| você / ele / ela | — (no ending) | fazer |
| nós | -mos | fazermos |
| vocês / eles / elas | -em | fazerem |
When the subordinate subject is different from the main subject, or when you simply want to make the subject explicit, the personal infinitive shines:
É melhor nós sairmos agora.
It's better for us to leave now.
É importante eles virem à reunião.
It's important that they come to the meeting.
O professor falou alto para todos ouvirem.
The teacher spoke loudly so that everyone could hear.
That last example is the key insight: para todos ouvirem expresses purpose ("so that everyone could hear") with a different subject (the students, not the teacher) — yet it needs no que and no subjunctive. Without the personal infinitive, you'd be forced into para que todos ouvissem. The infinitive route is shorter and, in Brazil, often the more natural choice in speech.
Replacing "que + subjunctive" with an infinitive
A great deal of subjunctive avoidance in everyday Brazilian Portuguese rides on the personal infinitive. Many sentences that "should" take que + subjunctive can be recast as an infinitive clause:
É preciso vocês assinarem o documento.
You all need to sign the document.
Trouxe um casaco para não passarmos frio.
I brought a coat so we wouldn't get cold.
The finite equivalents (É preciso que vocês assinem..., para que não passássemos frio) are perfectly correct, but the infinitive versions feel lighter and are extremely common. The rule of thumb: if you can name the subject and the verb can be an infinitive, you usually can swap. This is why mastering the personal infinitive does double duty — it also lets you sidestep some of the hardest subjunctive forms.
Ao + infinitive — "on / upon doing" (compact temporal)
The construction ao + infinitive compresses a whole "when…" clause into two words. It means "on doing / upon doing / as soon as," marking an action that coincides with or immediately precedes the main event.
Ao chegar em casa, liguei para a minha mãe.
On arriving home, I called my mother.
Ao abrir a porta, percebi que tinha esquecido as chaves dentro.
As I opened the door, I realized I'd left the keys inside.
It pairs naturally with the personal infinitive when the subject is explicit or plural:
Ao chegarmos ao topo, a vista era de tirar o fôlego.
When we reached the top, the view was breathtaking.
Impersonal or personal? A quick decision
Use the impersonal (bare) infinitive when the subject is the same as the main clause or generic. Use the personal (inflected) infinitive when the subordinate subject is different, plural, or you want to state it explicitly.
| Situation | Form | Example |
|---|---|---|
| Same subject | impersonal | Saí sem fazer barulho. |
| Different / explicit subject | personal | Saí sem os meninos fazerem barulho. |
| Plural "nós" | personal | É melhor irmos embora. |
Common Mistakes
❌ Antes de saindo, apaguei as luzes.
Incorrect — after a preposition Portuguese uses the infinitive, not the gerund.
✅ Antes de sair, apaguei as luzes.
Before leaving, I turned off the lights.
❌ É melhor nós sair agora.
Incorrect — with the explicit subject 'nós,' the infinitive must inflect: sairmos.
✅ É melhor nós sairmos agora.
It's better for us to leave now.
❌ O professor falou alto para todos ouvir.
Incorrect — the plural subject 'todos' requires the personal infinitive ouvirem.
✅ O professor falou alto para todos ouvirem.
The teacher spoke loudly so everyone could hear.
❌ Para eu fazer isso, é importante eu ter tempo.
Awkward — when the subject is first-person singular 'eu,' the infinitive stays bare; the form is correct but overusing 'eu' twice is clumsy.
✅ Para eu fazer isso, preciso de tempo.
For me to do that, I need time.
❌ Ao chegamos ao topo, a vista era linda.
Incorrect — 'ao' takes an infinitive, so the inflected personal infinitive 'chegarmos,' not the indicative 'chegamos.'
✅ Ao chegarmos ao topo, a vista era linda.
When we reached the top, the view was lovely.
Key Takeaways
- After a preposition, Portuguese uses the infinitive (never the gerund): antes de sair, sem pensar.
- The personal infinitive lets a clause keep its own subject without going finite — é importante eles virem — a feature English and Spanish lack.
- It is a primary tool for avoiding the subjunctive: para não passarmos frio instead of para que não passássemos frio.
- Ao + infinitive is a compact "on/upon doing," equivalent to a quando clause but shorter and smoother.
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Start learning Portuguese→Related Topics
- The Personal Infinitive: OverviewB1 — Portuguese's signature feature — an infinitive that carries person and number endings, letting infinitive clauses take their own subject.
- Personal Infinitive after PrepositionsB1 — How and when to inflect the infinitive after prepositions like para, sem, antes de, and em vez de when the clause has its own subject.
- Personal vs Impersonal InfinitiveB1 — How to decide whether to leave the infinitive bare or inflect it for person — the rule turns on whether the infinitive has its own, distinct subject.
- Personal Infinitive Replacing Subjunctive ClausesB2 — How Brazilian Portuguese uses the personal infinitive as a more concise, modern-sounding alternative to que + subjunctive clauses.
- Purpose Clauses (Para Que, A Fim de Que)B1 — How to express goals and intentions — para + infinitive for shared subjects, para que + subjunctive for different subjects, and the formal a fim de variants.