What is Infinitive Phrase

An infinitive form of a verb is the base form of a verb. The infinitive form of the verb is usually preceded by the preposition to. An infinitive phrase is a phrase that contains an infinitive, its complements and/or modifiers. Infinitive phrases always begin with the infinitive, and they can function as nouns, adjective and adverbs. As nouns, infinitive phrases can act as both subjects and objects.

Functions of Infinitive Phrase

Noun as Subject:

To become the president of the country is his ambition.

To give up now seems a waste of time.

Noun as Object:

The only alternative is to commit suicide.

She likes to sing old songs.

Adjective:

He gave me a book to read on the train.

I taught him the easiest way to draw a man.

Adverb:

I went to the library to return the books.

She opened the door to reveal a huge dragon.

She likes to sing songs.

Examples of Infinitive Phrase

He agreed to help the children.

To become a pilot is his greatest ambition.

She gave me a movie to write a review on.

They are trying to avoid the teacher.

The principal refused to lower the standard of the test.

Kyle wants to join a karate class.

We lacked the determination to continue this path.

His sister likes to watch cartoons.

Although many infinitives are preceded by the participle to, some infinitive verbs are not preceded by to. When the main verb of a sentence is a modal verb, the infinitive verb drops the preposition to.

He should see a doctor.

They might finish work early.

Other words such as make, feel, hear, see, help, let, and watch, also cause this effect. These verbs also take a direct object.

I saw her go home.

She helped me make a kite.

Punctuation with Infinitive Phrases

Commas should be used at the end of an infinitive phrase if the phrase is at the beginning of the sentence and functions as an adverb.

To improve your spelling, you must read more books.

To buy something to eat, he spent his last dollar.

Commas should be used on the either sides of the infinitive phrase if it breaks the flow of the sentence.

This color, to be perfectly honest, doesn’t suit your complexion.

Apart from these instances, punctuation is not needed for an infinitive phrase.

Infinitive Phrases vs Prepositional Phrases

Some people might confuse prepositional phrases with infinitive phrases as they also can begin with the preposition to. In such situation, the main difference between prepositional phrases and infinitive phrases is that the preposition to is followed by a verb in the infinitive phrase.

They go to the theater. – Prepositional phrase

He wants to go home. – Infinitive phrase