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Verbs that keep 'a' before an infinitive

In English, to sits in front of almost every infinitive: learn to swim, help to clean, force someone to leave. Portuguese has no single word that does this job. Some verbs take just an infinitive, some take de, and a large group takes a. That last group includes verbs of teaching, learning, helping, encouraging, persuading and forcing: ensinar a, aprender a, ajudar a, obrigar a.

English speakers often drop the a and say aprender nadar. It seems logical: if querer nadar works without anything in between, why not aprender nadar? The answer is that the a belongs to the verb itself, so it has to be learned together with it.

Word list
ajudarA1 to help ajudar alguém a + infinitive aprenderA1 to learn aprender a ler convidarA2 to invite convidar a entrar ensinarA2 to teach ensinar alguém a conduzir aconselharB1 to advise aconselhar alguém a + infinitive auxiliarB1 to help auxiliar alguém a + infinitive convencerB1 to convince convencer alguém a ficar persuadirB1 to convince persuadir alguém a aceitar recusar-seB1 to refuse recusar-se a pagar atrever-seB2 to dare atrever-se a perguntar desafiarB2 to challenge desafiar alguém a competir forçarB2 to force forçar alguém a assinar inspirarB2 to inspire inspirar alguém a escrever (to inspire someone to write) negar-seB2 to refuse negar-se a fazê-lo obrigarB2 to force obrigar alguém a sair tenderB2 to tend tender a esquecer encorajarC1 to motivate encorajar alguém a tentar incentivarC1 to motivate incentivar alguém a participar motivarC1 to motivate motivar alguém a estudar
How it works

The pattern is verb + a + infinitive. Many of these verbs push or guide another person, so the person comes first as the object and a links to the action: ensinar alguém a conduzir (teach someone to drive), obrigar alguém a sair (make someone leave). Others describe your own effort or attitude and have no object: aprender a ler, recusar-se a pagar.

Compare verbs that take just an infinitive, such as querer, poder, saber and decidir: quero sair, decidi ficar. English uses to after both groups, which is exactly why it is no help here.

Rule of thumb: if the verb means that someone teaches, learns, helps, pushes, persuades or forces, expect a before the next verb.

A minha mãe ensinou-me a nadar e ajudou-me a perder o medo.
(My mother taught me to swim and helped me lose my fear.)
The words
Teaching, learning and helping

Ensinar, aprender, ajudar and the more formal auxiliar are the everyday core of the group, and you will hear them from the start.

Este verão quero aprender a tocar guitarra.
(This summer I want to learn to play the guitar.)
Os enfermeiros auxiliam os doentes a levantar-se.
(The nurses help the patients get up.)
Encouraging, inviting and advising

Incentivar, motivar and encorajar all mean to encourage and all take a. So do convidar (invite) and aconselhar (advise).

O professor incentivou os alunos a participar.
(The teacher encouraged the students to participate.)
A senhora convidou-nos a entrar.
(The lady invited us to come in.)
O médico aconselhou-me a descansar uns dias.
(The doctor advised me to rest for a few days.)
Persuading

Convencer and persuadir both mean to convince someone to do something.

Consegui convencer o meu irmão a ficar mais um dia.
(I managed to convince my brother to stay one more day.)
Forcing and challenging

Obrigar and forçar mean to make someone do something. Desafiar (challenge) works the same way.

O chefe obrigou-nos a trabalhar no sábado.
(The boss made us work on Saturday.)
Eu desafio-te a correr até à praia.
(I challenge you to run to the beach.)
Refusing, daring and tending

These verbs have no person as object, but they still need a. Recusar-se and negar-se both mean to refuse, atrever-se means to dare, and tender means to tend.

Ele recusou-se a pagar a conta.
(He refused to pay the bill.)
Nunca me atrevi a perguntar.
(I never dared to ask.)
Eu tendo a esquecer os nomes das pessoas.
(I tend to forget people's names.)
Watch out

The typical mistake is simply leaving out a: ensinou-me nadar or recusou-se pagar. Always keep it. With a pronoun at the end, it stays too: recuso-me a fazê-lo.

Some verbs have alternatives:

  • Convidar is also very common with para, especially in Brazil: convidar para jantar.
  • Aconselhar can also take que + subjunctive: aconselho que esperes.
  • Convencer and persuadir use de que when you convince someone that something is true, not to do something.
  • In informal Brazilian speech you may hear ajudar without a. The version with a is always correct.

In Brazil the pronoun usually comes before the verb, but the a stays in place:

Ela me ensinou a nadar.
(She taught me to swim.)

Related expressions like habituar-se a and levar alguém a follow the same pattern.

Summary

English to is not a reliable guide. When a verb means teaching, learning, helping, encouraging, persuading, forcing, refusing or daring, put a before the next verb: aprender a ler, ajudar alguém a limpar, obrigar alguém a sair, recusar-se a pagar. Verbs like querer and poder take no a, so learn each verb together with its preposition.