Infinitives: A complete guide to understanding and using the base verb form

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Verbs are the heartbeat of any language, driving action and meaning in every sentence. Among their many forms, infinitives stand out as a foundational yet versatile element of English grammar.

Whether you are a student mastering the basics or a writer refining your style, understanding how to use “to-infinitives” and “bare infinitives” is essential for clear communication. This guide explores the definition, functions, and rules of infinitives with practical examples.

Also included:

The Infinitive Quiz
The Infinitive Cheat Sheet

The Ultimate Guide on Nouns

Nouns are the foundation of every sentence you write. This is part of the Ultimate Guide, which explores every category and rule, providing you with the tools to identify, use, and master them with total confidence.

What is an infinitive?

An infinitive is the base form of a verb, typically preceded by the word “to.” It functions as the “neutral” version of a verb because it is not conjugated; it isn’t tied to a specific tense (past, present, or future) or a specific subject.

The term originates from the Latin modus infinitivus, meaning “unlimited.” This is because the infinitive expresses the action of the verb without the limits of person or number.

Common examples of infinitives include:

To run
To eat
To think
To be

The two types of infinitives

Full infinitive (to-infinitive): The verb preceded by “to” (e.g., To sleep).
Bare infinitive: The base verb used without “to” (e.g., Sleep), often found after modal verbs.

How infinitives function in a sentence

Unlike standard verbs, infinitives are “verbals.” This means they are formed from a verb but can function as nouns, adjectives, or adverbs.

1. Infinitives as nouns

An infinitive can act as the subject or the object of a sentence.

As a subject: “To learn is a lifelong journey.”
As a direct object: “Sarah loves to paint.”
As a subject complement: “His only goal is to succeed.”

2. Infinitives as adjectives

When an infinitive modifies a noun, it acts as an adjective.

“Give me something to eat.” (Modifies the noun “something”)
“She has a great desire to travel.” (Modifies “desire”)

3. Infinitives as adverbs

An infinitive acts as an adverb when it modifies a verb or an adjective, usually to express purpose.

Modifying a verb: “He stayed late to help.” (Explains why he stayed)
Modifying an adjective: “I am happy to meet you.” (Explains the feeling of being “happy”)

Key rules for using infinitives

To ensure your writing is grammatically correct, follow these specific guidelines regarding word order and verb pairing.

Verbs followed by the infinitive

Certain English verbs must be followed by a full infinitive rather than a gerund (-ing form). Common examples include agree, decide, hope, plan, promise, and want.

Correct: “They decided to leave.”
Incorrect: “They decided leaving.”

When to use the bare infinitive

You should omit the “to” in the following scenarios:

After modal verbs: Words like can, should, must, will, and might always take the bare infinitive. (e.g., “I can run,” not “I can to run.”)
After causative verbs: When using let, make, or help, use the bare infinitive. (e.g., “Let her go.”)

How to negate an infinitive

To make an infinitive negative, simply place the word “not” immediately before the “to.”

Example: “He told me not to worry.”

Understanding split infinitives

A split infinitive occurs when an adverb is placed between “to” and the verb. While older grammar rules forbade this, modern English (and the Oxford English Dictionary) accepts it for better flow or emphasis.

Classic example: “To boldly go where no one has gone before.”

Infinitives vs. gerunds

One of the most common challenges in English grammar is choosing between an infinitive (to walk) and a gerund (walking). While they often cover similar ground, the meaning can shift depending on the verb used.

Verb Example	Used with Infinitive	Used with Gerund
Stop	“He stopped to smoke.” (He paused his walk to have a cigarette.)	“He stopped smoking.” (He quit the habit entirely.)
Remember	“Remember to call her.” (Don’t forget the future task.)	“I remember calling her.” (I have a memory of doing it in the past.)
Try	“Try to open the door.” (Make an effort to do it.)	“Try opening the door.” (Experiment with the door as a solution.)

Frequently asked questions about infinitives

An infinitive phrase includes the infinitive plus any objects or modifiers. For example, in the sentence “To read a book is relaxing,” the phrase is “To read a book.”

Yes. Using an infinitive as a subject is common in formal writing or proverbs, such as “To err is human; to forgive, divine.”

Infinitives can be modified for time and voice:

Passive infinitive: “I want to be heard.”
Perfect infinitive: “He is lucky to have finished on time.”

Summary

Infinitives are the “limitless” base of English verbs. By mastering their use as nouns, adjectives, and adverbs, you can add variety and precision to your writing. Whether you are avoiding common mistakes with modal verbs or deciding when to split an infinitive for emphasis, these rules provide the structure needed for advanced fluency.

For more on verb forms, you may want to explore our guides on Gerunds or the Difference between Gerunds and Infinitives.

Appendix

The Infinitive Quiz

Infinitive mastery quiz

Test your knowledge of English infinitives!

The Infinitive Master Cheat Sheet

1. The core formula

Full Infinitive: To + Base Verb (e.g., To explore)
Bare Infinitive: Base Verb (e.g., Explore)

2. When to use which? (Quick-Logic Table)

Context	Form to use	Example
After Modals (can, will, should)	Bare Infinitive	“I should go.”
Expressing Purpose (why?)	To-Infinitive	“I called to ask.”
After ‘Let’ or ‘Make’	Bare Infinitive	“Let him stay.”
Following Adjectives	To-Infinitive	“It’s easy to see.”
As a Subject	To-Infinitive	“To wait is hard.”

3. The “Big Three” meaning changers

Some verbs change their entire meaning depending on whether you use an infinitive or a gerund.

Forget:
- To-Infinitive: Forget a future task (“Don’t forget to pay the bill.”)
- Gerund: Forget a past memory (“I’ll never forget paying that bill.”)
Regret:
- To-Infinitive: Sad to give bad news (“I regret to tell you…”)
- Gerund: Sad about a past action (“I regret telling him the secret.”)
Try:
- To-Infinitive: Make an effort (“Try to open the jar.”)
- Gerund: Experiment with a method (“Try opening the window for fresh air.”)

4. Advanced variations (Cheat list)

Negative: Not + to + verb (“Try not to fall.”)
Passive: To + be + past participle (“I want to be chosen.”)
Perfect: To + have + past participle (“He seems to have left.”)
Continuous: To + be + -ing (“I’d love to be sleeping right now.”)

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Infinitives: A complete guide to understanding and using the base verb form

The Ultimate Guide on Nouns