Infinitives: What they are and what they do in English

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. Defined as the base form of a verb, usually paired with “to,” infinitives like “to run,” “to think,” or “to dream” transcend simple action, taking on roles as nouns, adjectives, or adverbs. Their flexibility, coupled with specific rules and variations like bare infinitives or split forms, makes them both essential and intriguing. This exploration unpacks what infinitives are, how they function, and the guidelines that shape their use, offering a clear path to understanding their power in everyday language.

What are infinitives?

An infinitive is the base form of a verb, typically preceded by the word “to.” It comes from the Latin [modus] infinitivus, which means unlimited. We commonly use infinitives every day. For example, “to run,” “to sing,” and “to write” are common infinitives. It’s the verb in its most basic, unconjugated form, not tied to a specific tense, person, or number. Infinitives can function as nouns, adjectives, or adverbs in a sentence, making them highly versatile.

There’s also a “bare infinitive,” which is the base verb without “to” (e.g., “run” instead of “to run”), used in specific grammatical contexts.

What do infinitives do?

Infinitives allow verbs to take on roles beyond simple actions. Depending on their function, they can:

1. Act as a noun:
   • Subject: To learn is important.
     • “To learn” is the subject of “is.”
   • Direct Object: I want to dance.
     • “To dance” is the object of “want.”
   • Subject Complement: My goal is to succeed.
     • “To succeed” complements “goal.”
2. Act as an adjective:
   • Modifies a noun: She has a desire to travel.
     • “To travel” describes “desire.”
3. Act as an adverb:
   • Modifies a verb, adjective, or another adverb: He came to help.
     • “To help” explains why “he came.”
   • She’s eager to start.
     • “To start” modifies “eager.”
4. Express purpose or intention:
   • Example: I study to improve my skills.
     • “To improve” shows the purpose of “study.”

Rules for using infinitives

Infinitives follow specific guidelines to fit naturally into sentences:

1. Formation: Most infinitives are “to” + base verb.
   • Examples: to eat, to sleep, to be.
   • Bare infinitives (without “to”) occur after certain verbs or modals (see below).
2. After certain verbs: Some verbs require an infinitive as their object, such as “want,” “decide,” “hope,” “plan,” “promise,” “agree,” and “learn.”
   • Correct: She decided to leave.
   • Incorrect: She decided leaving.
3. After modal verbs (bare infinitive): Modal verbs like “can,” “must,” “should,” “will,” etc., are followed by a bare infinitive.
   • Correct: I can run fast.
   • Incorrect: I can to run fast.
4. After verbs like “help,” “make,” “let” (bare infinitive): Certain causative or permissive verbs use the bare infinitive.
   • Example: She made him laugh.
   • Example: Let me try.
5. After adjectives: Infinitives often follow adjectives to explain them.
   • Example: It’s hard to understand.
     • “To understand” modifies “hard.”
6. Infinitive phrases: Infinitives can include objects or modifiers, forming a phrase that still serves as a noun, adjective, or adverb.
   • Example: To read a good book is my plan.
     • The phrase “to read a good book” is the subject.
7. Negation: Add “not” before the infinitive to make it negative.
   • Example: I decided not to go.
8. Split infinitives: While traditionally frowned upon, it’s acceptable in modern English to insert an adverb between “to” and the verb for emphasis or clarity.
   • Example: To boldly go where no one has gone before.
     • “Boldly” splits “to” and “go.”
9. Versus gerunds: Some verbs can take either an infinitive or a gerund, but the meaning may change:
   • Stop to smoke: Pauses an action to start smoking (infinitive = purpose).
   • Stop smoking: Quits the habit (gerund = noun).
10. Perfect, passive, or continuous forms: Infinitives can take advanced forms:
    • Perfect Infinitive: To have finished feels great.
    • Passive Infinitive: She wants to be heard.
    • Continuous Infinitive: He seems to be working hard.

Additional notes

• Omission of “to”: In some cases, “to” is implied but omitted, especially after “and” in parallel structures.
  • Example: I need to eat, sleep, and study (implied: to study).
• Question words: Infinitives pair with “how,” “what,” “where,” etc., in instructional contexts.
  • Example: I don’t know how to fix this.

Summary

Infinitives may start as the humble base of a verb, but their ability to morph into nouns, adjectives, or adverbs reveals their true linguistic agility. Whether expressing purpose, modifying meaning, or standing as the subject of a sentence, infinitives bring depth and nuance to communication. Mastering their rules—from when to drop “to” to how they differ from gerunds—unlocks a richer grasp of English, blending structure with creativity. As a bridge between action and intention, infinitives prove that even the simplest verb form can carry limitless potential, inviting learners and speakers alike to explore their endless possibilities.

Further study:

• Gerunds
• Gerunds vs. Infinitives