As the most basic of verb forms, the Spanish infinitive is widely used, even more so than its English counterpart. Since it has some characteristics of both verbs and nouns, its usage can be quite flexible. Following are the most common uses of the infinitive, along with sample sentences and links to lessons:
As the subject of a sentence: When it functions as the subject of a sentence, the infinitive functions much as it does when used as the subject in an English sentence, although it is often translated using the English gerund. Thus the sentence "Nadar es difícil" could be translated as either "To swim is difficult" (English infinitive) or "Swimming is difficult" (English gerund).
Infinitives used as nouns are masculine. Usually, when the subject infinitive is used to refer to general situations, no definite article (in this case el) is needed (although some speakers optionally include it). But when referring to specific instances, the article is often used. Thus, el isn't used in the above sample sentence, but it is here: El nadar a través del río era un movimiento fatal. (Swimming across the river was a fatal move.)
- (El) fumar es una de las peores cosas que los niños pueden hacer con sus cuerpos. Smoking is one of the worst things that children can do with their bodies.
- (El) votar es una obligación y un derecho. Voting is an obligation and a right.
- ¿De dónde procede este comprender? Where does this understanding come from?
As the object of a preposition: The use of infinitives after prepositions is another example of them functioning as nouns. Although the rule isn't consistently applied, the use of the definite article is usually optional. Spanish infinitives coming after prepositions are almost always translated using the English gerund.
- El error está en pensar que el inglés tiene las mismas estructuras que el español. The mistake is in thinking that English has the same structures as Spanish.
- El hombre fue expulsado de restaurante por comer demasiado. The man was kicked out of the restaurant for eating too much.
- Nacimos para estar juntos. We were born to be together.
In forming the periphrastic future: As explained in the lesson on the nonsimple future tenses, an infinitive can follow a present-tense form of ir a to form a very common type of future tense. Voy a cambiar el mundo. I'm going to change the world.
As a substitute for the subjunctive mood: The most common sentence structure calling for use of the subjunctive mood is one in the form of "subject + main verb + que + subject + subjunctive verb." However, if the two subjects in the sentence are the same, it is normal to drop the que and replace the second verb with an infinitive. This can be seen in a simple example: In "Pablo quiere que María salga" (Pablo wants Mary to leave), the two subjects are different and the subjunctive is used. But if the subjects are the same, the infinitive is used: Pablo quiere salir. (Pablo wants to leave.) Note that the English infinitive is used in both translations; you'd make a mistake to imitate English in that regard.
- Esperamos obtener mejores resultados. We hope to get better results. (With different subjects, the subjunctive would have been used: Esperan que obtengamos mejores resultados. They hope we get better results.)
- Yo prefería hablar con la pared. I would prefer to talk with the wall.
- Javier niega querer salir del Barcelona. Javier denies wanting to leave Barcelona.
The infinitive may also substitute for the subjunctive following impersonal statements:
- No es necesario comprar un computador caro para realizar tareas sencillas. It isn't necessary to buy an expensive computer in order to accomplish simple tasks.
- No es probable ganar la lotería. It isn't likely to win the lottery.
Although generally the subjunctive is used following que when when the main subject and the subordinate subject are different, an exception can occur with various verbs of influence such as dejar (to let), mandar (to mandate) and prohibir (to prohibit). In such sentences, the person performing the action is represented by an indirect-object pronoun.
- Deserté porque me ordenaron matar a civiles. I deserted because they ordered me to kill civilians.
- Déjanos vivir en paz. Let us live in peace.
- Mis padres me prohibieron tener novio. My parents prohibited me from having a boyfriend.
- Le hicieron andar con los ojos vendados. They made him walk blindfolded.
One way of analyzing the above sentences is to view the infinitive as the object of the main verb and the indirect object as representing the person affected by the main verb's action.
To follow certain verbs: Numerous verbs, too many to list here, are routinely followed by an infinitive. Structurally, the infinitive functions as an object of the verb, even though we may not think of it that way. Among these verbs are poder, which is usually thought of as an auxiliary verb.
- No puedo creer que su nombre no está en este reporte. I can't believe his name isn't in this report.
- Los científicos lograron crear células del cerebro humano. The scientists succeeded in creating human brain cells.
- Los dos fingieron estar enfermos para ingresar al área de emergencia del hospital. The two pretended to be sick in order to enter the hospital emergency room.
- Debemos cuidar el planeta Tierra. We ought to care for the planet Earth.
- Mi amiga no sabe estar sola. My friend doesn't know how to be alone.
With verbs of perception: In a sentence construction that's difficult to analyze, the infinitive can be used to indicate that someone was a witness (such as by hearing or seeing) to a completed action.
- Vimos volar un florero por la ventana. We saw a vase fly through the window.
- Nunca te vi estudiar. I never saw you study.
- Te oyeron cantar el himno. They heard you sing the hymn.