When we talk about writing and grammar, we often come across a structure that might sound tricky, but it’s something we use all the time—infinitive clauses. These are simple yet versatile tools that help us express ideas clearly and effectively.

In this post, we’ll break down what infinitive clauses are, how they work, and how you can use them in your own writing.

What is an Infinitive Clause?

An infinitive clause is a group of words that start with an infinitive verb.

The infinitive verb is the base form of a verb with the word to in front of it, like to eat, to learn, or to help.

An infinitive clause can also have other words with it, such as a subject or modifiers, to make it more detailed.

♦ Example: I need to finish my homework.
♦ Example: She plans to travel next year.

In these examples, to finish and to travel are the infinitive verbs, and together with the other words, they form an infinitive clause.

Functions of Infinitive Clauses

Infinitive clauses can serve different roles in a sentence. We’ll look at the most common ways they’re used.

Infinitive Clauses as the Subject

An infinitive clause can act as the subject of a sentence. This means that the action in the infinitive clause is the main topic of the sentence.

♦ Example: To learn a new language takes time.

In this sentence, To learn a new language is the subject—it’s what the sentence is about.

Infinitive Clauses with Subjects

Sometimes, infinitive clauses can have their own subject. This happens when we want to be clear about who is doing the action of the infinitive.

♦ Example: It’s important for her to study hard.

In this sentence, her is the subject of the infinitive clause to study hard. The infinitive clause explains what is important, but it also tells us who needs to study.

Infinitive Clauses as the Object

We often use infinitive clauses as the object of a verb, meaning they receive the action of the verb. In this situation, we regard the noun or pronoun within the clause as the subject of the infinitive.

♦ Example: She wants to become a teacher.

Here, to become a teacher is what she wants, so it’s the object of the verb wants. Even though she appears to be in the objective case, they are the subjects of the infinitive verbs.

Infinitive Clauses as a Complement

An infinitive clause can also work as a complement, completing the meaning of a noun or adjective.

♦ Example: He was happy to help.

In this case, to help explains what made him happy, completing the idea.

Related Reading: Understanding Verb Inflection

Using To and For

How do we use to and for.

Infinitive Clauses Without “To”

There are situations where certain verbs are followed by infinitive clauses without the word to. These verbs often indicate permission, causation, or sensory perception.

♦ Example: What makes him cry? (Compare: What causes him to cry?)
♦ Example: I let him sleep. (Compare: I allowed him to sleep.)

In these examples, pack, cry, and sleep are infinitives without to, but the construction remains an infinitive clause.

Typically, an infinitive does not make a direct assertion because it lacks a subject. However, in an infinitive clause, the noun or pronoun preceding the infinitive acts as the subject, making an assertion in much the same way a that-clause would.

♦ Example: I wished him to go makes as clear an assertion as I wished that he should go.

Although it might appear that him is the direct object of the verb wished, it is actually a component of the larger structure him to go, which makes up the complete object. Wished actually refers to the whole infinitive clause, not just the pronoun.

The verb dare allows you to use the infinitive with or without ‘to’. For example:

Infinitive Clauses with “For”

The preposition for can introduce an infinitive clause and perform various roles in a sentence.

Examples:

♦ For us to delay would be a mistake. (This clause functions as the subject of the sentence.)
♦ Our plan is for the boat to shoot the rapids. (Here, the clause is a predicate nominative, renaming plan.)
♦ I see no solution except for them to apologize. (The clause is the object of the preposition except.)

In these examples, the noun or pronoun (us, them) is the subject of the infinitive, and the full infinitive clause takes on different roles in the sentence.

Predicate Pronouns in Infinitive Clauses

Predicate pronouns in infinitive clauses follow the verb to be and must agree with the subject of the infinitive in the objective case.

This differs from the typical rule of using the nominative case for pronouns following to be in regular sentences.

Examples:

♦ I believed him to be the leader (the pronoun him is in the objective case because it is the subject of the infinitive to be).
Compare this to
♦ I believed that he was the leader (where he is in the nominative case as it is the subject of the finite verb was).

Compare this to
♦ We know the author to be her (uses her in the objective case because it follows to be in the infinitive clause).

♦ We know that the author is she (uses she in the nominative case as it follows the finite verb is).

Understanding this distinction helps avoid confusion in sentence structure, especially when using infinitive clauses.

When using an infinitive clause with to be, remember that the pronoun after to be should match the subject of the infinitive. Basically, it should be in the objective case after an infinitive.

♦ Example: I believed it to be her. (Objective case, agreeing with it)
♦ Example: We know the author to be him. (Objective case, agreeing with the author)

Compare these with sentences using that-clauses, where the pronouns would be in the nominative case

♦ Example: I believed that it was she.
♦ Example: We know that the author is he.

When analyzing a sentence, the pronoun in the infinitive clause agrees with the subject of the infinitive, which is in the objective case.

Related Reading: Unlocking the Power of Nouns in Writing

Common Uses of Infinitive Clauses

We can use infinitive clauses to express purpose, explain reasons, or show desires. Let’s look at some examples of how they function in different situations.

Expressing Purpose

Infinitive clauses are often used to explain why someone does something. We use them to show purpose or intention.

♦ Example: She exercises every day to stay healthy.

The infinitive clause to stay healthy explains the purpose of her exercising.

Explaining Reasons

You can use infinitive clauses to explain why you do things.

♦ Example: He left early to avoid traffic.

In this sentence, to avoid traffic explains the reason he left early.

Showing Desires, Hopes, or Plans

When we talk about our desires, hopes, or plans, we often use infinitive clauses.

♦ Example: I hope to visit Japan next year.

The infinitive clause to visit Japan shows what I hope to do.

Key Takeaways

1. Understand when to use an infinitive clause: You often use infinitive clauses after verbs like want, need, expect, hope, plan, and decide.
2. Use infinitive clauses to express purpose: Infinitive clauses often express why something is done.
3. Watch for common verbs that take infinitive clauses: Verbs like advise, allow, ask, tell, persuade, and warn commonly take infinitive clauses.
4. Infinitive clauses can follow “for”: Infinitive clauses often follow the preposition “for” to show purpose or desired action.
5. Use infinitive clauses after “too” and “enough”: After “too” or “enough,” infinitive clauses show extremes or sufficiency.
6. Use infinitive clauses with passive voice: They can be used in passive structures.

7. Be mindful of negating infinitives: To negate an infinitive clause, place “not” before the infinitive.
8. Use caution with infinitives after modals: After modal verbs (can, should, will, etc.), the infinitive appears without “to.”
9. Use infinitive clauses after adjectives: They can follow adjectives to explain why someone feels a certain way.
10. Distinguish between gerunds and infinitives: Some verbs can be followed by either gerunds (-ing verbs) or infinitives, but the meaning may change.

Last Words on Using Infinitive Clauses

Infinitive clauses are a flexible way to simplify complex sentences by replacing that-clauses. Whether following verbs of wishing, commanding, or perceiving, or used with the preposition for, they provide a neat, compact structure in English grammar.
Understanding their role helps clarify who is doing what in a sentence, making communication clearer and more efficient.

Happy writing!

Linda

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