An infinitive is a verbal consisting of the word to plus a verb (in its simplest "stem" form) and functioning as a noun, adjective, or adverb. The term verbal indicates that an infinitive, like the other two kinds of verbals, is based on a verb and therefore expresses action or a state of being. However, the infinitive may function as a subject, direct object, subject complement, adjective, or adverb in a sentence. Although an infinitive is easy to locate because of the to + verb form, deciding what function it has in a sentence can sometimes be confusing.
To wait seemed foolish when decisive action was required. (subject)
Everyone wanted to go. (direct object)
His ambition is to fly. (subject complement)
He lacked the strength to resist. (adjective)
We must study to learn. (adverb)
Be sure not to confuse an infinitive—a verbal consisting of to plus a verb—with a prepositional phrase beginning with to, which consists of to plus a noun or pronoun and any modifiers.
Infinitives: to fly, to draw, to become, to enter, to stand, to catch, to belong
Prepositional Phrases: to him, to the committee, to my house, to the mountains, to us, to this address