to-infinitive

El infinitivo con to, to-infinitive, es usado:

• para expresar propósito

          Carl called to talk about our plans for tomorrow.

• después de ciertos verbos (agree, appear, decide, expect, hope, plan, promise, refuse, etc)

          They expect to finish the building work this afternon.

• después de would like, would prefer, would love, etc para expresar una preferencia específica

          I would prefer to go out for dinner tonight.

• después de adjetivos que describan sentimientos/emociones (happy, sad, glad, etc), expresan buena o mala disposición (willing, eager, reluctant, etc), relativos al carácter de una persona (clever, kind, etc) y los adjetivos lucky y fortunate.

          I was sad to hear that Carol had lost her job.

       Con adjetivos que se refieren al carácter podemos usar una construcción 

       impersonal.

          It was kind of you to help Andrea with her essay.

• después de too/enough

          It isn't warm enough to go out without a coat.

• para hablar sobre un evento inesperado, normalmente con only.

          I finally arrived at the airport only to find that my flight had been 

          cancelled.

• con it+be+adjective/noun

          It was easy to find the house after all.

• después de be+first/second/next/last etc

          She was the first person to congratulate me after the game was over.

• después de verbos y expresiones como ask, learn, explain, decide, find out, want, want to know, etc cuando van seguidos de una palabra de pregunta (question word)

          The maths teacher explained how to solve the problem.

       Pero hay excepciones como why que va seguido por sujeto + verbo y 

       NO por un infinitivo.

          I wonder why she didn't tell us.

• en expresiones como to tell you the truth, to be honest, to sum up, to begin with, etc

          To tell you the truth I didn't expect that you would come.

       Nota: cuando dos to-infinitives están unidos por and u or, el to del 
       segundo infinitivo puede ser omitido.

          I would like to go and see what is happening for myself.

El infinitivo sin to, infinitive without to, es usado:

• después de verbos modales

          Beth can speak German and Italian.

• después de los verbos let, make, see, hear and feel pero usamos el infinitivo con to en la forma pasiva de los anteriores verbos. Compara las siguientes oraciones:

          They made him fill out a lot of forms.

          He was made to fill out a lot of forms.

       Nota: cuando see, hear y watch están seguidos por la forma -ing no 

       hay cambio en la pasiva.

          He saw me talking to Anna.

          I was seen talking to Anna.

• después de had better y would rather

            We had better take the train because the traffic is very bad at the 

          moment.

• help puede ir seguido de to-infinitive o infinitive without to

          She helped me (to) choose the carpet for the living room.