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Infinitive verbs in English: What are they and when are they used?

By: revel arroway, Isabel McKay Wed Oct 02 2024
English
Verbs

The infinitive form of a verb in English is the generic form of the verb that we use to talk about the idea of an action outside of a particular place or time.

  • The full infinitive form of a verb in English is to + the root.

    • to be

    • to do

    • to have

  • Sometimes, we leave out the word to and use just the root as the infinitive instead. This is called a “bare infinitive” or a “zero infinitive” or an “infinitive without to.”

In this post, we will take you through the structure of English infinitives and introduce you to some of the main uses of infinitive verbs in English. In that discussion, we’ll cover some cases where it might be tricky to choose between the full infinitive and other forms of the verb (like the participle or bare infinitive).

Are you ready to learn about infinitives in English? Let me teach you the basics!

Table of Contents

    How to form an infinitive in English?

    To form the full infinitive of an English verb, add the word to before the “dictionary” form of the verb (also known as the “root” of the verb)

    to

    root

    Root form
    Infinitive form
    Example

    be

    to be

    I want to be an actor.

    want

    to want

    Patty decided to go to the cinema.

    go

    to go

    What do you have left to do this afternoon?

    do

    to do

    I don’t know what to do!

    get

    to get

    Are you going to get a new car?

    have

    to have

    Peter hopes to have some extra time today.

    Tip

    In an infinitive, the word to does not have any meaning. It is only there to show that the verb is infinitive.

    There are some specific situations where English speakers delete the word to from an infinitive verb. When this happens we call it a “bare” infinitive, and it looks just like the root by itself.

    • Can she sew?

    • I made her jump.

    • I watched him clean the sink.

    An infinitive phrase (sometimes called an infinitive clause) is an infinitive verb and a few associated words that complete its meaning (like objects or prepositional phrases) after the infinitive to complete its meaning:

    I asked him…

    • …to clean the bathroom.

    • …to leave the cup on the counter.

    • …to come to the park.

    When to use the infinitive with ‘to’ in English?

    In English, the main times we use full infinitive verbs (with to) are in the following cases:

    • To complete the meaning of a verb

      We often use infinitives after verbs of thinking, speaking, or feeling, to complete their meaning. Verbs that are used with full infinitives usually follow three main patterns:

      • verb + infinitive

        She wanted to go to Harvard.

        → The subject of the infinitive is the same as the subject of the sentence.

        Some common verbs in this group: want, love, pretend, begin, ask, try, seem,...

      • verb + object + infinitive

        He told her to go to Harvard.

        → The subject of the infinitive is the object of the main verb.

        Some common verbs in this group: need, allow, get, force, order, ask, choose,...

      • verb + for + object + infinitive

        We planned for our son to go to Harvard.

        → The subject of the infinitive is the object of the preposition for.

        Some common verbs in this group: ask, mean, would like/love, arrange,...

      Learning which verbs are used with infinitives and which pattern(s) each verb follows will take some practice. Luckily, we have a whole article for you about how to use infinitives after verbs in English that can give you much more detailed tips!

    • With adjectives

      We also use infinitives with certain adjectives, especially those that express a feeling, ability, or opinion. Here are some common cases where we use infinitive verbs with adjectives:

      • The adjective describes the subject and the infinitive gives more information about the adjective:

        • She was able to climb the rope.

          → she = able (the skill is “climb a rope”)

        • I was sorry to hear about your accident.

          → I = sorry (because I heard about your accident)

      • The adjective describes the infinitive verb. There are several ways to build sentences that do this:

        • Starting with "empty it":
          (common)

          It’s easy to drive this car.

          → driving this car = easy
          (sentence about the action)

        • Starting with an infinitive:
          (rare)

          To drive this car is easy.

          → driving this car = easy
          (sentence about the action)

        • Starting with the object:
          (common)

          This car is easy to drive.

          → driving this car = easy
          (sentence about the object of the infinitive)

      Learning which adjectives are used with infinitives and how to build sentences with adjectives and infinitive verbs will likely take some practice! Luckily, our post on using adjectives with infinitive verbs in English can give you some great advice!

    • With nouns

      We often use infinitive verbs with nouns for acts of speech or thought, opportunity, or ability. Here are the two main reasons that English nouns are associated with infinitives:

      • The infinitive is a topic of speech, thought, opportunity, or ability:

        • The suggestion to plant these flowers came from Tom. (speech)

        • It was time to go to class. (opportunity)

        • She had a desire to travel the world. (thought)

        • Maria has the ability to sing beautifully. (ability)

      • The noun describes or represents the infinitive action. Just like with adjectives, there are several ways to build these sentences:

        • Starting with “empty it”:

          It’s a pleasure to teach Maria.

        • Starting with an infinitive:

          To trust Bill was a mistake.

        • Starting with the object:

          You are a delight to talk to.

      Learning which English nouns are used with infinitives and how to build sentences using nouns and infinitive verbs will likely take some practice. But check out our post on using English nouns with infinitive verbs for some great tips!

    • To describe a purpose or goal

      Infinitive verbs can be used to describe the purpose of something or goal of an action.

      You can describe the purpose or goal of any action using an infinitive. For example:

      • Andre attended his daughter’s play to show her that he loved her.
        In order to show her that he loved her, Andre attended his daughter’s play.

      • To pass the exam, I studied my notes.
        I studied my notes so as to pass the exam.

        → To learn more about the phrases in order and so as, check out our post on reason, purpose, and result clauses in English!

      Or you can describe the intended future use of any noun. For example:

      • Andre has a couch to sell.

      • We have a lot of work to finish.

    When to use a bare infinitive (without ‘to’) in English?

    We use bare infinitives without to in a few different situations:

    • After modal verbs

      We use bare infinitive verbs after modal verbs, like can, could, will, would, shall, should, might, may, and must:

      • Maria can run.

      • Kendra should go to the party.

      • He must be our teacher!

      The expressions would rather and had better are also used before the bare infinitive.

    • After a few common verbs

      We use a bare infinitive (rather than an infinitive with to) after a few kinds of main verbs in English as well. Use this structure:

      subject

      main verb

      object

      bare infinitive

      In all cases, the object of the main verb is the subject of the infinitive.

      • Most verbs of perception (e.g. see, watch, hear, feel,...) take a bare infinitive:

        • I saw the prisoner escape!

        • Bill heard the car start.

        • Andre felt his heart beat.

      • A few common verbs of causation (let, make, bid...) also take bare infinitives:

        • I let him go.

        • Andre made him do the dishes.

        • We bade the servant carry the bags.

      For more details, examples, and advice on how to use these verbs, check out our post on verbs that take infinitives in English!

    Are there other uses of the root form in English?

    In English, a bare infinitive is just the root of a verb. We use this root in a few other contexts, for example:

    Usually, in these uses, we will just call the verb form “the past/present simple form,” “the imperative form,” or “the subjunctive form,” because these are specialized uses of the root, but some teachers may still call this form of the verb the “bare infinitive” because they look the same.

    Passive, perfect, and continuous infinitives: What are they and when to use them?

    Passive infinitives, perfect infinitives, and continuous infinitives are all types of “complex” infinitives. Complex infinitives are infinitive verbs that use an auxiliary verb (have or be). There are three main kinds of complex infinitives in English:

    • A passive infinitive is the infinitive of an English passive verb. Passive infinitives have this form:

      to be

      past participle

      ↳ An English past participle is usually root + -ed.

      We use passive infinitives when we want to talk about an action which is done to the subject, rather than an action that the subject does.

      • Simple infinitive:

        Mildred wished to forget her bad day.

        → Mildred wished that Mildred would forget the day.

      • Passive infinitive:

        Mildred wished to be forgotten.

        → Mildred wants others to forget about Mildred.

    • A perfect infinitive: the infinitive of a verb in the perfect aspect. Perfect infinitives have this form:

      to have

      past participle

      Use these to emphasize that you are talking about a completed or finished action.

      • Perfect Infinitive:

        Mildred was sorry to have insulted her friend.

        → We are only talking about how Mildred felt after she insulted her friend.

    • A continuous infinitive (or progressive infinitive) is the infinitive of a verb in the continuous aspect. Continuous infinitives have this structure:

      to be

      present participle

      ↳ An English present participle is usually root + -ing.

      Use these to emphasize that you are talking about an action that happens at the same time as the other actions in the sentence.

      • Simple infinitive:

        Mildred is happy to watch TV.

        → In general, the act of watching TV makes Mildred happy.

      • Continuous Infinitive:

        Mildred is happy to be watching TV.

        → Mildred is watching TV now and she is happy about it.

    More rarely, infinitive verbs can be formed using more than one auxiliary, which creates combinations like:

    • A perfect continuous infinitive:

      Mildred would have liked to have been watching TV, but instead she was doing homework.

    • A continuous passive infinitive:

      The meeting seems to be being held in the conference room.

    • A perfect passive infinitive:

      Mildred wished to have been allowed to go to the movies.

    • A perfect continuous passive infinitive (very rare, but possible!):

      When her father arrived, Mildred was playing a game with her classmates. She would have preferred to have been being taught calculus when he got there, but her teacher was sick that day.

    What is a split infinitive?

    A split infinitive is when an adverb comes between to and the root of an infinitive verb:

    • I want you to quickly finish the job.

    • She expects you to finally visit her this summer.

    English speakers often split infinitives. One famous example is from the introduction of “Star Trek”:

    “To boldly go where no man has gone before.”

    Today, most teachers and editors will say that it is okay to split infinitives.

    However, in the past English speakers were taught that you should never split an infinitive, so some old-fashioned editors and teachers will still say that splitting infinitives is an error. To be safe, avoid splitting infinitives if there is another phrasing that works just as well:

    • I want you to quickly finish the job. → I want you to finish the job quickly.

    • You may wish to not drink spoiled milk. → You may wish not to drink spoiled milk.

    But if you feel you need to split the infinitive, it is fine to do so!

    Summary

    In this post we covered the formation and use of infinitive verbs in English. We saw:

    • Infinitives have the form: to + root (to see), but bare infinitives are just the root (see).

    • Infinitives with to are used:

      • To complete the meaning of a verb (I want to leave.)

      • To complete the meaning of an adjective (I was able to see him.)

      • To complete the meaning of a noun (I made a choice to go hiking.)

      • To describe the purpose of an action or noun (I have money to spend.)

    • Bare infinitives are used:

      • After modal verbs (could, can, should…)

      • To complete the meaning of a few common verbs:

        • verbs of perception or imagination (see, hear, picture…)

        • a few causative verbs (make, let, bid, help)

    • Complex infinitives (e.g. passive infinitives, perfect infinitives, continuous infinitives…) use auxiliary verbs.

    • In split infinitives, an adverb comes between to and the root.

    Ready to practice what you’ve learned? Check out our English infinitive verb activity sheet! Or review this longer list of English verbs that take gerunds and infinitives as objects.

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