Here is the best news in the Brazilian Portuguese verb system: forming the personal infinitive is completely uniform. You take the infinitive — any infinitive, regular or irregular — and add a fixed, tiny set of person endings. There are no exceptions. Not one. After the maze of irregular preterites and present subjunctives, the personal infinitive is a flat, predictable rule you can learn in five minutes. This page shows you exactly how to build it and warns you about the one form it can be confused with.
The endings
Start from the plain infinitive (falar, comer, partir) and add:
| Subject | Ending |
|---|---|
| eu | — (nothing) |
| tu (regional) | -es |
| você / ele / ela | — (nothing) |
| nós | -mos |
| vocês / eles / elas | -em |
The eu and você/ele/ela forms add nothing — they're identical to the plain infinitive. The tu form (-es) is mostly literary or regional in Brazil; in everyday Brazilian Portuguese, você replaces tu, so you'll rarely produce it. That leaves just two endings you genuinely have to learn: -mos for nós and -em for vocês/eles/elas.
The three regular classes
The endings are identical across all three verb classes — they attach to the full infinitive, so the -ar / -er / -ir vowel is preserved.
| Subject | falar | comer | partir |
|---|---|---|---|
| eu | falar | comer | partir |
| tu | falares | comeres | partires |
| você / ele / ela | falar | comer | partir |
| nós | falarmos | comermos | partirmos |
| vocês / eles / elas | falarem | comerem | partirem |
É melhor falarmos com o gerente agora.
It's better for us to speak with the manager now.
Trouxe um lanche para vocês comerem no caminho.
I brought a snack for you all to eat on the way.
No caso de partirem antes, deixem a chave na portaria.
In case you all leave earlier, leave the key at the front desk.
Irregular verbs are NOT irregular here
This is the part worth tattooing on your memory. A verb can be wildly irregular in the present, the preterite, the future subjunctive — and still be perfectly regular in the personal infinitive. That's because the personal infinitive is built on the infinitive, which is by definition the regular stem. There are no irregular personal infinitives in the language.
| Subject | ser | ir | fazer | ter | pôr |
|---|---|---|---|---|---|
| eu | ser | ir | fazer | ter | pôr |
| você / ele / ela | ser | ir | fazer | ter | pôr |
| nós | sermos | irmos | fazermos | termos | pormos |
| vocês / eles / elas | serem | irem | fazerem | terem | porem |
Note the orthography of pôr: the infinitive keeps its circumflex (pôr, to distinguish it from the preposition por), but once an ending is added the stress shifts and the accent drops — pormos, porem. This is the one small spelling wrinkle, and it follows the spelling rules, not a verb irregularity.
É essencial sermos honestos uns com os outros.
It's essential for us to be honest with one another.
Eles trouxeram documentos para fazerem o cadastro.
They brought documents in order to do the registration.
Antes de irmos embora, vamos pagar a conta.
Before we leave, let's pay the bill.
The trap: personal infinitive vs future subjunctive
Here's the one genuine source of confusion, and it's worth being honest about. For regular verbs, the personal infinitive is identical in form to the future subjunctive. Look:
| Subject | Personal infinitive (falar) | Future subjunctive (falar) |
|---|---|---|
| eu | falar | falar |
| nós | falarmos | falarmos |
| vocês / eles | falarem | falarem |
They are spelled and pronounced exactly the same. Only context tells them apart: the future subjunctive appears after conjunctions like quando, se, assim que (quando falarmos — when we speak); the personal infinitive appears after prepositions like para, antes de, sem (para falarmos — for us to speak). You don't actually have to decide which is which to produce the right form — for regular verbs they coincide.
For irregular verbs, the two diverge sharply, and this is where the trap snaps shut. The future subjunctive of an irregular verb is built on its (irregular) preterite stem, while the personal infinitive is always built on the plain infinitive.
| Verb | Personal infinitive (nós) | Future subjunctive (nós) |
|---|---|---|
| ser | sermos | formos |
| ter | termos | tivermos |
| fazer | fazermos | fizermos |
| ir | irmos | formos |
| pôr | pormos | pusermos |
So ser gives sermos as a personal infinitive but formos as a future subjunctive — completely different words.
É bom sermos pacientes.
It's good for us to be patient. (personal infinitive — in a subject clause, not after a conjunction)
Quando formos ao Rio, te aviso.
When we go to Rio, I'll let you know. (future subjunctive — after 'quando')
A note on the written accent
Watch the accents when an -ir verb has a stressed i, and when adding -em shifts stress:
- sair → sairmos, saírem — the í in saírem takes an acute because it's the stressed vowel in a paroxytone ending in -em.
- pôr → pormos, porem — circumflex drops once endings are added.
These follow the general accentuation rules of Portuguese; they are not verb irregularities.
Common Mistakes
❌ É importante nós sairem cedo.
Incorrect — the subject is 'nós', so the ending is '-mos': sairmos.
✅ É importante nós sairmos cedo.
It's important for us to leave early.
❌ Antes de eles serem... não: antes de eles formos.
Incorrect — 'formos' is the future subjunctive. After 'antes de', use the personal infinitive: 'serem'.
✅ Antes de eles serem avaliados, vamos conversar.
Before they are evaluated, let's talk.
❌ Para nós tivermos sucesso, precisamos planejar.
Incorrect — 'tivermos' is the future subjunctive. After 'para', use the personal infinitive: 'termos'.
✅ Para nós termos sucesso, precisamos planejar.
For us to succeed, we need to plan.
❌ Trouxe comida para vocês comer.
Incorrect — with the plural subject 'vocês', the ending is '-em': comerem.
✅ Trouxe comida para vocês comerem.
I brought food for you all to eat.
❌ É essencial sermos honesto.
Adjective-agreement slip — with 'nós', the adjective is plural: honestos.
✅ É essencial sermos honestos.
It's essential for us to be honest.
Key Takeaways
- Personal infinitive = infinitive + (—, -es, —, -mos, -em). The tu (-es) form is regional/literary in Brazil.
- The only two endings you actively learn are -mos (nós) and -em (vocês/eles).
- There are no irregular personal infinitives — ser → sermos/serem, ter → termos/terem, ir → irmos/irem, all built on the plain infinitive.
- For regular verbs the personal infinitive looks identical to the future subjunctive; context disambiguates.
- For irregular verbs they differ: ser = personal infinitive sermos vs future subjunctive formos; ter = termos vs tivermos.
Now practice Portuguese
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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.
- Futuro do Subjuntivo: FormationA2 — How to build the future subjunctive in Brazilian Portuguese — derived from the third-person plural preterite, and why it looks deceptively like the infinitive.
- Future Subjunctive vs Future IndicativeB1 — Why 'quando você chegar' (future subjunctive) pairs with a main-clause future like 'eu vou te ligar' — how the two halves of a future sentence each pick their own form.
- The Regular (Impersonal) InfinitiveA1 — The unchanging dictionary form of the verb — falar, comer, partir — and the five main places it appears in Brazilian Portuguese.