The infinitive is the form of a verb that is listed in the dictionary. In English, the infinitive commonly begins with to. Here are some examples:

• to run
• to want
• to be
• to have
• to become

The infinitive form of a verb is almost always used after the conjugated form of another verb.

• I came to talk to you. (Came is in its conjugated form, so I used the infinitive, to talk, to complete the sentence.)
• Robert tried to call her after lunch.
• Did you ask to speak with the director?

Note that with some verbs, such as must, let, should, can, etc., the word to in the infinitive form of the verb is not used directly afterwards:

• I must run in order to win the race.
• Just let them tell their story.
• What do you think we should do?