Infinitives: What they are and what they do in English

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 are the verb’s raw form, dressed up with “to” (or not), and they stretch across noun, adjective, and adverb roles. The rules hinge on verb compatibility, context, and whether “to” stays or drops. They’re about purpose, description, or action-as-thing, contrasting with gerunds (which are always nouns).

Further study:

• Gerunds
• Gerunds vs. Infinitives

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