What Are Infinitives? Learn Types and How To Use Them

Infinitives, in essence, are verbals formed by combining the word "to" with a verb in its most basic form. 

This unique structure allows infinitives to serve multiple grammatical functions within a sentence, functioning as nouns, adjectives, or adverbs. 

In some instances, infinitives require an actor to act, while in others, they can stand alone without a specific subject. 

It's easy to spot an infinitive, however, it requires close attention to identify its function in the sentence.

Types of Infinitives

Infinitives are a part of speech that can take on different forms based on how they're used in a sentence. Here are some common types:

Full Infinitive

The full infinitive is the most common form of an infinitive in English grammar. It consists of the word "to" followed by the base form of the verb. It can be used to convey purpose, becoming the infinitive of purpose.

Full infinitives are used in a wide range of contexts, including after verbs, adjectives, and nouns, to convey various meanings and functions within a sentence.

For example:

• She loves to dance.
• He decided to go to the beach.
• They plan to travel around the world.

Bare Infinitive

The bare infinitive, also known as the base infinitive, is an infinitive form of a verb without the preceding "to." 

It is used in specific situations, such as after modal verbs (can, may, must, etc.) and certain causative verbs (make, let, have, etc.). It is also used with imperatives and after verbs of perception. Bare infinitives often denote actions that are immediate, direct, or mandatory. Here are some examples:

• You should go home now.
• Let him try again.
• They made her sing a song.

Split Infinitive

A split infinitive occurs when an adverb or other word is inserted between "to" and the base form of the verb. 

Its usage in formal writing is usually not encouraged. However, it may be used in cases when the adverb doesn’t suit anywhere else. For instance, 

“She decided to quickly finish her assignment.”

In this sentence, the adverb “quickly” is inserted between “to” and the base form of the verb “finish.” The split infinitive emphasizes the speed of her action.

Perfect Infinitive

The perfect infinitive is formed by adding "to have" before the past participle of the verb. It is used to indicate an action that was completed before another action or a certain point in time. 

Perfect infinitives often convey the sequence of events or actions and are commonly used in conjunction with modal verbs to express possibility, necessity, or obligation. For instance,

• She seems to have finished her homework.
• He appears to have forgotten his keys.
• They seem to have arrived early.

Continuous or Progressive Infinitive

The continuous infinitive is formed by adding "to be" before the present participle (the "-ing" form) of the verb. 

It indicates an action that is ongoing or in progress at a certain point in time. Continuous infinitives are used to convey duration, continuity, or simultaneous actions, similar to the progressive aspect in verb tenses. Here are some instances:

• She plans to be studying all night.
• He hopes to be working on the project tomorrow.
• They expect to be traveling during the holidays.

Passive Infinitive

The passive infinitive is formed by adding "to be" before the past participle of the verb. 

It is used to express passive voice, where the subject of the sentence is the recipient of the action rather than the doer. Passive infinitives are often employed to shift focus or emphasize the object or recipient of the action. For example,

• The car needs to be repaired.
• The report has to be submitted by Friday.
• The cake is ready to be eaten.

Gerunds and Infinitives

Gerunds are verb forms ending in "-ing" that, like infinitives, can function as nouns. 

Gerunds are used when actions or activities are the subject, object, or complement of a sentence, such as "Swimming is great exercise".  They often denote ongoing actions or habits. 

Infinitives, on the other hand, are used to express purpose, intent, or desire, as seen in "She wants to swim every day." 

Though primarily different, they both can act as nouns such as, swimming or to swim.

What's the Difference Between Infinitives and Prepositional Phrases?

When discerning between infinitives and prepositional phrases, it's crucial to understand how they employ the word "to." While "to" commonly functions as a preposition, its role in infinitives differs from its use in prepositional phrases.

In prepositional phrases, "to" consistently requires a noun as its object:

We're driving to the countryside tomorrow.

She gave a gift to her friend.

Here, "to" directly precedes nouns ("the countryside," "her friend") within the prepositional phrases.

Conversely, in infinitives, "to" introduces a verb, regardless of whether the infinitive acts as a noun:

They plan to explore new destinations next summer.

He hopes to win the competition.

In these examples, "to" introduces infinitives ("to explore," "to win"), where it's followed by verbs (explore, win).

What is an Infinitive Phrase?

An infinitive phrase is a group of words that includes an infinitive and any accompanying modifiers, objects, or complements (a phrase). Infinitive phrases function as nouns, adjectives, or adverbs within a sentence, providing additional information or context.

Structure of an Infinitive Phrase

Infinitive phrases typically consist of the following components:

The Infinitive: The main verb in its base form, preceded by "to."

Modifiers: Words or phrases that provide additional information about the infinitive.

Objects or Complements: Nouns, pronouns, or phrases that receive the action of the infinitive or complete its meaning.

Here are some examples of infinitive phrases:

• To swim in the ocean is her favorite activity. (Subject of the sentence)
• She needs a book to read during the flight. (Direct object of the verb "needs")
• He bought a hat to wear to the party. (Modifying the noun "hat")
• The tools to fix the car are in the garage. (Describing the tools)
• He left early to catch the train. (Modifying the verb "left," indicating purpose)
• She studied hard to pass the exam. (Describing how she studied)

Verbs Associated with Infinitives

Verbs in English can be followed by infinitive objects, either with or without actors. The choice of whether to include an actor depends on the verb's meaning and usage within the sentence structure.

Verbs that Take Infinitive Objects Without Actors:

Some verbs are followed directly by infinitives without mentioning the doer of the action. These verbs typically express actions, plans, or states that don't require a specific actor.

Examples of such verbs include:

Plan: "She plans to travel next month."

Begin: "They began to renovate their house."

Here’s a list of these verbs:

• Plan
• Begin
• Fail
• Decide
• Hope
• Want
• Choose
• Forget

Verbs that Take Infinitive Objects with Actors

Other verbs are followed by infinitives with explicit actors, indicating who performs the action mentioned in the infinitive phrase. These verbs often involve advising, reminding, or forcing someone to do something.

Examples of such verbs include:

Advise: "She advised him to seek professional help."

Remind: "He reminded her to lock the door before leaving."

Here’s a list of verbs infinitives objects with actors:

• Advise
• Remind
• Force
• Encourage
• Persuade
• Instruct
• Allow
• Require

Verbs that Can Use Either Pattern

Some verbs have the flexibility to take infinitive objects with or without actors, depending on the context and intended meaning of the sentence. These verbs allow for versatile usage in expressing actions or intentions.

Examples of such verbs include:

Ask: "She asked to leave early." (without actor) / "She asked him to leave early." (with actor)

Expect: "They expect to win the competition." (without actor) / "They expect him to win the competition." (with actor)

Here are some such verbs:

• Ask
• Expect
• Like
• Need
• Prefer
• Teach
• Tend
• Enable

How To Use Infinitives

Infinitives, the versatile components of English grammar, serve a multitude of functions within sentences. Here are some ways they can be used in sentences:

Infinitives As Nouns

Infinitives, despite being verbals, can function as nouns within a sentence, providing essential meaning and serving various roles.

• The subject of a Sentence

Infinitives can serve as the main subject of a sentence. They express the general idea of an action without specifying who is performing it. For example:

To swim in the ocean is refreshing.

Here, “to swim” acts as the subject of the sentence.

• The object of a Verb

Infinitives can also function as the direct object of a verb. They receive the action performed by the main verb. For instance:

She wants to travel the world.

In this case, “to travel” is the object of the verb “wants.”

• The object of a Preposition

Infinitives can follow prepositions and act as their objects. These prepositional phrases provide additional information. Example:

He is excited about the opportunity to learn new skills.

Here, “to learn” is the object of the preposition “about.”

As Adjectives

Infinitives can also function as adjectives, modifying nouns. They describe the purpose or quality of the noun. Consider:

The book to read is on the shelf.

In this sentence, “to read” describes the type of book.

As Adverbs

Infinitives can play the role of adverbs, providing additional information about the verb. They answer questions like “why,” “how,” or “to what extent.” Example:

She worked hard to succeed.

Here, “to succeed” explains the purpose or goal of her hard work.

Test Your Knowledge - Find The Correct Infinitive

Give this infinitive exercise a try to test what you’ve learned above:

In summary, you've learned a lot about infinitives and how they work in English sentences. You've also had some practice with exercises to help you remember what you've learned. 

But if you're still not feeling confident about your grammar, you can try out our grammar checker tool. It's an easy way to make sure your writing is mistake-free and looks professional. 

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