Personal Infinitive for Clarity

The personal infinitive is a distinctive feature of Portuguese. While a regular infinitive (impersonal) is used for general actions, the personal infinitive is typically used when the subordinate clause has a different subject than the main clause.

1. Formation:
Take the dictionary form (impersonal infinitive) and add these endings:

• Eu: (no ending)
• Tu: -es
• Ele/Ela/Você: (no ending)
• Nós: -mos
• Vós: -des
• Eles/Elas/Vocês: -em

2. The Rule of Different Subjects:
When a sentence has two different subjects, the personal infinitive is used specifically in prepositional phrases or after impersonal expressions (it is not a universal rule, as many main verbs require a conjunction + subjunctive instead). While the impersonal infinitive is the default when the subjects are the same, you can still use the personal infinitive with the same subject to add emphasis, clarify a dropped pronoun, or when the infinitive is separated from the main verb. Note that with verbs of perception (ver, ouvir, sentir) or causation (fazer, mandar, deixar), the impersonal infinitive is standard and required when the subject of the infinitive is a clitic object pronoun (e.g., Vi-os sair - I saw them leave). When the subject is a full noun, both the impersonal and personal infinitives are perfectly correct and widely used (e.g., both Vi os meninos sair and Vi os meninos saírem are standard).

3. After Impersonal Expressions:
When using impersonal expressions (such as é importante, é preciso, or é bom) followed by a specific subject, the personal infinitive is used to clarify who is performing the action (e.g., É importante vocês estudarem - It is important for you to study).

4. Common Prepositional Triggers & Word Order:
When there is a change in subject, or when the subject is explicitly stated for emphasis, the personal infinitive is triggered by prepositions such as:

• para (so that / for)
• sem (without)
• antes de (before)
• depois de (after)
• ao (upon / when)
• por (because of / due to)
• até (until)

Word Order: While the explicit subject often goes between the preposition and the verb (e.g., para nós estudarmos - for us to study), Portuguese word order is highly flexible. It is equally natural and very common to place the subject after the verb, especially with full noun subjects (e.g., depois de chegarem os convidados - after the guests arrive).

5. Prepositions vs. Conjunctions:
It is important to distinguish between the personal infinitive and the future subjunctive. While they look identical for regular verbs, the personal infinitive is triggered by prepositions (like para - for, or sem - without), whereas the subjunctive is triggered by conjunctions (like se - if, or quando - when).

6. Note on Irregular Verbs:
The personal infinitive always uses the dictionary stem (e.g., sermos - for us to be, termos - for us to have, dizerem - for them to say). This distinguishes it from the future subjunctive, which uses the preterite stem (e.g., formos - if we are/go, tivermos - if we have, disserem - if they say).

7. Regional Differences:
The personal infinitive is ubiquitous in everyday European Portuguese. In spoken Brazilian Portuguese, however, speakers often prefer finite subjunctive clauses (e.g., para que eles façam - so that they do, instead of para eles fazerem - for them to do) or rely more heavily on the impersonal infinitive.

8. The 'No Contraction' Rule:
In standard written Portuguese, prepositions should not contract with the subject of a personal infinitive. For example, you should write apesar de ele saber (despite him knowing), not apesar dele saber.