The infinitive is the basic, unconjugated form of a verb, sometimes called the name of the verb. In English the infinitive is to + verb: to talk, to eat, to leave, etc. The Spanish infinitive is a single word with one of the following endings: -ar, -er, or -ir: hablar, comer, salir, etc. We usually learn Spanish verbs in the infinitive, since that is what you start with in order to conjugate them.

The Spanish infinitive is often translated to the English gerund, as you’ll see in the examples below.

The infinitive an be used several different ways without any conjugation:

1. As a noun: the subject or object of a sentence

Mentir no es buena idea.   Lying is not a good idea.
Aprender es importante.   Learning is important.

2. After a conjugated verb, the infinitive can be used

    a) with a preposition

Vamos a estudiar.   We’re going to study.
Acabo de salir.    I just left.
Salgamos depués de comer.   Let’s leave after eating. 
La biblioteca es perfecta para estudiar.   The library is perfect for studying.

    b) without a preposition

Me gusta bailar. I like dancing.
Prefieren venir con nosotros. They prefer coming with us.
Los vi jugar. I saw them play.

    c) with que

Tienes que comer.   You have to eat.
Hay mucho que hacer.   There’s a lot to do.

3. In place of the subjunctive when the main clause has

    a) the same subject as the subordinate clause

Tiene miedo que llegué tarde.*
 ==> Tiene miedo de llegar tarde. 
  He’s afraid of arriving late.
Estoy contenta que tenga razón.*
 ==> Estoy contenta de tener razón.
  I’m happy to be right.

* These are grammatically incorrect. When the subject is the same, you *must* use the infinitive.

    b) an impersonal subject (if the subject is implied)

Es importante que trabajes.
 ==> Es importante trabajar.
  It’s important to work.
No es necesario que vengan.
 ==> No es necesario venir.
  It’s not necessary that they come (They don’t need to come).

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