An infinitive is the most basic form of a verb. It is “unmarked” (which means that it is not conjugated for tense or person), and it is preceded by the particle to, as in to run, to read, to swim, etc.
Infinitives are known as non-finite verbs, meaning they do not express actions being performed by the subjects of clauses. Instead, infinitives function as nouns, adjectives, or adverbs to describe actions as ideas.
Infinitives are distinct from a similar construction known as bare infinitives or the base forms of verbs, which are simply infinitives without the particle to. Although nearly identical, we use them in different ways than “full” infinitives, which we’ll look at later in this section.
Infinitives are used to express an action as a concept, rather than what is being done or performed by the subject of a clause. In this way, they can function as nouns, adjectives, or adverbs—that is, nearly any role in a sentence except that of a main verb.
Infinitives can stand on their own to complete these functions, or they can work together with their own predicates (any additional information that modifies or completes them) to form infinitive phrases. Infinitive phrases function as a nouns, adjectives, or adverbs as a single, holistic unit.
(In the examples in this section, infinitive phrases have been put in bold, while the infinitive verbs that begin them are in italics.)
Making infinitives negative
To make an infinitive or infinitive phrase negative, we use the word not before the infinitive. We can also put greater emphasis on not by placing it after to.*
(*This creates what is known as a split infinitive—an infinitive that has an adverb between to and the base form of the verb. While some traditional grammar guides state that this should never be done, in reality there is no such “rule” in English; it is perfectly grammatical to split an infinitive, and in many cases it sounds more natural to do so.)
Infinitives as nouns
The subject performs, occupies, or controls the action of the verb.
- “To err is human; to forgive is divine.”
- “To study mathematics at Harvard was her ultimate dream.”
- “To live in the city means adjusting to a completely different lifestyle.”
As direct objects
A direct object is a person or thing that directly receives the action of the verb in a clause. An infinitive that acts as the object of another verb is sometimes known as a verb complement.
Remember that intransitive verbs do not take direct objects, so you will only find infinitives used as the objects of transitive verbs.
- “I’m not going unless you agree to go with me.”
- “You appear to be correct.”
- “Please be quiet; I’m trying to study.”
- “They’re attempting to solve the equation.”
- “Let me know if you decide to leave early.”
- “We hope to go in the near future.”
- “We rarely manage to get out of the house for the night.”
As objects in reported speech
When we use reported speech, we often use infinitives as the direct object of a “reporting verb” to express what was said or asked in the past. For example:
- “He asked to help us fix the car.”
- “She said not to answer the phone.”
- “He demanded to speak to the manager.”
- “They offered to take me to the airport.”
- “I promised to buy her a diamond ring.”
- “He threatened to report me to the police if I didn’t give him back the money.”
Certain verbs do not make sense with only a direct object, especially when that direct object is a person. More information is required about the object’s relationship with the verb to form a complete thought. This extra information is known as the object complement.
An infinitive can also act as an object complement, which is word or group of words that describe, rename, or complete the direct object of the verb. For example:
- “I don’t expect you to approve of my decision.”
- “She’s forcing me to work through the weekend.”
- “We need you to make a few more copies.”
- “Janet’s father wants her to go to Harvard.”
- “I would like the boss to see these reports.”
- “He persuaded me to marry him.”
- “They taught me (how) to work the photocopier.”
We often use infinitives as object complements in reported speech to express what someone said to or asked of someone. For example:
- “He asked me to help him.”
- “She told me not to answer the phone.”
Gerunds vs. Infinitives
Certain verbs can take either gerunds or infinitives as direct objects. In some cases, this results in no difference in meaning. For example:
“I like to hike on the weekend.”
“I like hiking on the weekend.”
“She loves to read.”
“She loves reading.”
“They hate to get bad news.”
“They hate getting bad news.”
“I prefer to go out on a Friday than to stay at home.”
“I prefer going out on a Friday than staying at home.”
In other instances, however, the meaning of the clause is significantly changed as a result. For instance, the verbs remember, forget, try, and stop can have both infinitives and gerunds as direct objects, but the meaning changes depending on which is used. For example
“I remembered to close the window.” (I didn’t forget to do it.)
“I remember closing the window.” (I clearly recall it.)
“I forgot to meet John earlier.” (I didn’t remember to do it.)
“I forget meeting John earlier.” (I don’t remember this fact even though it happened.)
“Try to get some rest.” (Attempt to do this.)
“Try getting some rest.” (Try this as a possible solution to the problem.)
“I stopped to drink water before bed.” (I interrupted what I was doing to drink water.)
“I stopped drinking water before bed.” (I don’t drink water before bed anymore.)
Predicate nouns are a subset of a larger category known as subject complements (including predicate pronouns and predicative adjectives), which rename or re-identify the subject after a linking verb (usually a form of the verb be). For example:
- “All I want is to be left alone.”
- “The best thing in life is to spend time with those you love.”
- “The best we can hope for is to break even.”
Infinitives as adjectives
When infinitives are used as adjectives, they function in a similar way to relative clauses (also known as adjective clauses), providing more information about a noun or pronoun that they appear directly after. For example:
- “This is a good place to start reading.” (To start reading modifies the noun place.)
- “Give your brother something to play with.” (To play with modifies the pronoun something.)
- “Find a friend to help you study.” (To help you study modifies the noun friend.)
Infinitives as adverbs
We can also use infinitives as adverbs to modify the main verb in a sentence, describing a reason why an action is, was, or will be done. Infinitives used in this way are often known as infinitives of purpose. For example:
- “I started running to improve my health.”
- We can also use the phrases in order and so as to add formal emphasis to an infinitive of purpose, as in:
- “We must leave now in order to catch our train.”
- “He’s been studying all week so as to improve his grades.”
Note that we do not use the preposition for before the infinitive; we only use for with a noun or noun phrase to create a prepositional phrase that modifies the verb to describe its purpose. Consider, for example, these three sentences:
- “I went to the supermarket to buy some bread.” (correct—infinitive phrase)
- “I went to the supermarket for some bread.” (correct—prepositional phrase)
- I went to the supermarket for to buy some bread.” (incorrect—preposition used with infinitive phrase)
We can also use infinitives in this way as isolated responses to questions asking why something is done or is the case. For example:
- Speaker A: “Why are you going to New York?”
- Speaker B: “To see the Empire State Building.”
- Speaker A: “Why did you turn on the TV?”
- Speaker B: “To watch the news.”
These responses are known as elliptical sentences, meaning that part of the sentence has been omitted because it is implied. In this case, the implied section is “because I wanted… .” As this element is implicitly understood, we often leave it out entirely and simply use the infinitive on its own.
Infinitives vs. Base Forms (Bare Infinitives)
The base form of a verb is simply the infinitive without the particle to—like an infinitive, it is uninflected for tense and person. Because of this similarity, the base form of a verb is often known as a bare infinitive, and some grammar guides and writers make little distinction between the two forms.
However, infinitives and base-form verbs function differently, so it is important to distinguish between them. An infinitive can be used in a sentence as a noun, an adverb, or an adjective, but it cannot act as a true verb that expresses the action of a subject.
The base form of a verb, on the other hand, can be used in conjunction with the auxiliary verb do to become negative or to form questions. They are also used with modal auxiliary verbs to express things like possibility, necessity, obligation and permission, as well as to create the simple future tense.
Verbs that take bare infinitives
The base form is also used after the direct object of certain action verbs, such as let, help, and make, as well as after verbs of the senses, such as hear, see, and feel.
Let’s look at some examples of these below. The bare infinitives (base forms) are in bold, while the main verbs are underlined and the direct objects are italicized:
- “Please let me go to the party, mom.” (Please give me permission to go.)
- “His father makes him study.” (His father forces him to study.)
- “Jack is helping me clean the garage.” (Jack is cleaning the garage with me.)
- “He heard me shout.” (He could that I was shouting.)
- “I saw her look in my direction.” (I could see that she was looking in my direction.)
- “I felt him touch my arm.” (I could feel that he touched my arm.)
(Note that these are not the only verbs that can be followed by bare infinitives.)
After had better
The base forms of verbs are also used after the phrase had better, which acts like the modal verb should to suggest a required or desirable action. For example:
- “You had better clean this up before your father gets home.”
- “I think we’d better go home soon.”
Bare infinitives can also follow the word why to form questions, as in:
- “Why study when I already know the material by heart?”
- “Why watch TV when we could play outside?”
These types of questions are called elliptical, which, as we saw above, means that part of the sentence has been left out because it is implied. The full questions might read:
- “Why should I study when I already know the material by heart?”
- “Why would we watch TV when we could play outside?”
Since the italicized parts of these sentences can be implied, they are sometimes left out entirely.