Infinitivo Impessoal vs Pessoal

The Infinitivo is one of the three formas nominais (nominal forms) verbs can have. These nominal forms do not express the verb tense, mode, and person by themselves, as they are dependent on the context in which they appear.
The infinitivo expresses the idea of an action and it could be thought of as the base form of the verb.
There are two types of infinitivo: Impessoal (Impersonal) and Pessoal (Personal). We’ll dive into each type below and explain the differences.

Infinitivo Impessoal

The Infinitivo Impessoal (impersonal infinitive) is invariable, meaning it appears without any conjugation as it doesn’t have a subject.
É obrigatório lavar as mãos. Washing hands is mandatory.
The example above is not referring to anyone specific, just to the general idea of “washing”.
However, the infinitive can also appear as the subject of a sentence itself.
Errar é humano. To err is human.
Amar é viver. To love is to live.
Again here, the verbs refer to the general idea of the action, rather than to a specific person doing the action.

Infinitivo Pessoal

The Infinitivo Pessoal (personal infinitive) differs because there is a known subject. It is formed by adding the terminations -es (tu) , -mos (nós), -des (vós) and -em (eles, elas, vocês) to the Infinitivo Impessoal. (Because the 2nd person plural vós is rarely used nowadays, we’ll focus our attention on the other three.)
The following table shows how the Infinitivo Pessoal is conjugated with three different verbs.

ir (to go) comer (to eat) falar (to speak)
eu ir comer falar
tu ires comeres falares
ele / ela / você ir comer falar
nós irmos comermos falarmos
eles / elas / vocês irem comerem falarem

As you can see, the 1st and 3rd person singular conjugations are the same as the Infinitivo Impessoal, which can sometimes be a little confusing. We’ll now look into how each one is used.

Using the Infinitive

Knowing which type of infinitive to use may not be as straightforward as you might think. Because linguists can’t reach a consensus on creating rules to regulate the use of infinitive, we’re going to show, instead, a list of the most common tendencies.

Impessoal

We use the infinitivo impessoal

  • When there’s no reference to a subject. (Or when the infinitive verb is the subject itself, as in the earlier examples).
É bom dançar. It's good to dance.
  • When the verb acts as a complement to a noun, verb, or adjective that needs a preposition:

Foram decisões fáceis de tomar. They were easy decisions to make.
The adjective (fáceis) needs a preposition (de), so you need to use the infinitivo impessoal.
Adjectives like fácil (easy), possível (possible), capaz (capable), bom (good), raro (rare), among others, followed by the preposition de, will also be followed by a verb in the infinitivo impessoal. Same goes for verbs like estar (to be), andar (to walk), ir (to go), ficar (to stay), and others, followed by the preposition a. Adjectives and verbs can also be followed by the prepositions para/por/que.
Estou a fazer o almoço. I'm making lunch.
Vou ter que sair. I'm going to have to leave.

  • In locuções verbais (phrasal verbs):

Queres comer em casa? You want to eat at home?
Fomos visitar Coimbra. We went to visit Coimbra.

  • When it depends on causative (express that an action causes a change in something else) and stative (express a state of being rather than an action) auxiliary verbs, either immediately following them or separated by a pronoun:

Mandem sair as pessoas da sala. Tell the people to leave the room.
Ela viu-o passar na rua. She saw him walking on the street.

Pessoal

We use the infinitivo pessoal

  • When the subject is clearly known and expressed:

Acho melhor tu ires com eles às compras.
É bom eles dançarem. It's good for them to dance.
Notice that this last example is similar to the one used above (É bom dançar), but by adding the subject eles, we had to switch to the infinitivo pessoal and conjugate the verb by adding -em.

  • When the subject is made known by the verb itself:

É melhor (vocês) irem para casa. It's better for you to go home.
É obrigatório (tu) lavares as mãos. It's mandatory for you to wash hands.
Unlike the previous example (É obrigatório lavar as mãos), which was not directed at any particular person, in this example we are referring to “you”, so we used the infinitivo pessoal and conjugated the verb by adding -es.
The decision of whether to use the impessoal or pessoal can get complicated, but the simplest way to start thinking about it is this: in general, if the focus is more on a particular subject doing the action, use the pessoal, and if the focus is more on the general action itself, use the impessoal.