5.1 Uses of the Infinitive

1. The use of the infinitive that can most easily cause comprehension problems is when it comes after the contraction al and is the equivalent of “upon” or “on” + present participle:
   

   Al llegar, veo a mis parientes.	Upon/On arriving, I see my relatives.
   Al terminar, vamos a salir a un restaurante.	Upon finishing, we’re going to go out to a restaurant.

   The above al (al llegar, al terminar) is not the same as the contraction al (a + el), which usually translates as “to the”: Vamos al concierto. (We’re going to the concert.)

2. Other uses, which seldom cause comprehension problems, include the following. As in English, Spanish routinely uses the infinitive form of the verb after a conjugated one:
   

   Lucía no desea cocinar.

   Lucía doesn’t want to cook.

3. The infinitive is the verb form used when the verb is the subject of the sentence. It is sometimes preceded by the masculine singular definite article, which is never translated. (The use or absence of the article does not change the meaning at all, however using the article makes slightly more formal Spanish.)
   

   (El) Leer ficción me interesa.	Reading fiction interests me.
   Nadar es uno de mis pasatiempos.	Swimming is one of my pastimes

4. The infinitive is the form of the verb you will see after a preposition in Spanish. The preposition is almost never translated*.
   

   Vamos a trabjar.	We are going to work.
   Salgo después de estudiar.	I go out after studying.
   Amenaza con salir.	He threatens to leave.
   Enrique me ayuda a aprender.	Enrique helps me to learn.
   Nos invita a ir.	She invites us to go.
   Tratamos de ayudar.	We try to help.

*One case in which the preposition happens to be translated in English is with the verb insistir: Insiste en hablar = she insists on speaking.