The infinitive phrase is one of the most flexible verbal constructions in English. Consisting of "to" plus the base form of a verb (along with any modifiers, objects, or complements), infinitive phrases can function as nouns, adjectives, or adverbs. This versatility makes them essential for expressing purpose, desire, intention, and description. In this guide, you'll learn every function of infinitive phrases, master the split infinitive debate, and understand when to use infinitives versus gerunds.
Table of Contents
What Is an Infinitive Phrase?
An infinitive is the base form of a verb preceded by "to": to run, to eat, to think, to be, to have. An infinitive phrase includes the infinitive plus any objects, complements, or modifiers associated with it.
Simple infinitive: "to sing"
Infinitive phrase: "to sing a beautiful song at the concert"
Components: infinitive ("to sing") + direct object ("a beautiful song") + prepositional phrase ("at the concert")
Unlike gerund phrases (which always function as nouns) and participial phrases (which always function as adjectives), infinitive phrases are uniquely versatile—they can function as nouns, adjectives, or adverbs depending on their role in the sentence.
Infinitive Phrases as Nouns
When functioning as nouns, infinitive phrases can serve as subjects, direct objects, or subject complements:
As Subject
"To learn a new language takes dedication."
"To travel the world is her lifelong dream."
"To forgive is divine."
In modern English, it's common to use "it" as a placeholder subject: "It takes dedication to learn a new language."
As Direct Object
"She wants to become a doctor." (Wants what?)
"They planned to leave early in the morning."
"I hope to finish the project by Friday."
"He decided to accept the job offer."
As Subject Complement
"Her goal is to graduate with honors."
"The best strategy is to save money consistently."
"My plan was to arrive before everyone else."
Infinitive Phrases as Adjectives
When functioning as adjectives, infinitive phrases modify nouns or pronouns, often indicating purpose or potential. They typically follow the noun they modify:
"She needs a place to study quietly." (modifies "place")
"He has a lot of work to finish before the deadline." (modifies "work")
"The decision to postpone the meeting was controversial." (modifies "decision")
"I need something to eat." (modifies "something")
"She was the first person to arrive at the office." (modifies "person")
Infinitive Phrases as Adverbs
When functioning as adverbs, infinitive phrases typically express purpose (why an action is performed), and they modify verbs, adjectives, or adverbs:
Expressing Purpose (Modifying Verbs)
"She went to the library to study for her exam." (Why did she go?)
"He exercises every day to stay healthy."
"They hired a tutor to help their son with math."
"I woke up early to catch the sunrise."
Modifying Adjectives
"She was happy to receive the good news." (modifies "happy")
"The puzzle is difficult to solve without help." (modifies "difficult")
"We were eager to begin the project." (modifies "eager")
Modifying Adverbs
"He ran fast enough to win the race." (modifies "enough")
"She spoke too quickly to be understood." (modifies "too")
The Split Infinitive Debate
A split infinitive occurs when a word (usually an adverb) is placed between "to" and the verb: "to boldly go," "to really understand," "to carefully examine."
Like the rule against ending sentences with prepositions, the prohibition on split infinitives is a grammar myth borrowed from Latin. In Latin, infinitives are single words and cannot be split. In English, the infinitive consists of two words, and splitting it is often the most natural and clear construction.
Split (natural): "She wanted to really understand the material."
Unsplit (awkward): "She wanted really to understand the material."
Unsplit (awkward): "She wanted to understand really the material."
Today, all major style guides accept split infinitives. Split them when it sounds natural; avoid splitting when it creates awkwardness or when the adverb can be placed elsewhere without changing the meaning.
Bare Infinitives (Without "To")
In certain constructions, the infinitive appears without "to." This is called a bare infinitive:
After modal verbs: "She can swim." "He should leave." "They might come."
After "let": "Let me help you."
After "make" (causative): "She made him apologize."
After "help" (optional): "He helped her (to) carry the boxes."
After perception verbs: "I watched her dance." "I heard him sing."
Verbs Followed by Infinitives
Many verbs require infinitive objects. Some take an infinitive directly, while others require a noun/pronoun between the verb and the infinitive:
Verb + Infinitive
want, need, hope, plan, decide, agree, promise, refuse, expect, learn, appear, seem, offer, pretend, manage, afford, fail, tend, wish, intend, prepare, choose, claim
Verb + Object + Infinitive
ask, tell, advise, allow, permit, encourage, expect, force, invite, order, persuade, remind, teach, urge, warn, want, need, help
"She asked him to help." (verb + object + infinitive)
"The teacher encouraged the students to participate."
"I advised her to see a doctor."
Infinitive vs. Gerund Phrases
The choice between infinitive and gerund depends on the main verb. Some verbs take only infinitives, some take only gerunds, and some accept both. When both are possible, the meaning may or may not change:
| Pattern | Example Verbs |
|---|---|
| Gerund only | enjoy, avoid, finish, mind, suggest, consider, deny, risk |
| Infinitive only | want, need, hope, decide, agree, promise, refuse, expect |
| Both (same meaning) | begin, start, continue, like, love, hate, prefer |
| Both (different meaning) | stop, remember, forget, try, regret |
Common Infinitive Patterns
Too + Adjective/Adverb + Infinitive
"The box was too heavy to lift."
"She spoke too softly to be heard."
Adjective/Adverb + Enough + Infinitive
"He is old enough to drive."
"She ran fast enough to qualify."
It + Be + Adjective + Infinitive
"It is important to exercise regularly."
"It was difficult to understand the instructions."
Practice Exercises
Identify the infinitive phrase and state its function (noun, adjective, or adverb):
- "To win the championship was their ultimate goal."
- "She went to the store to buy groceries."
- "He needs a partner to help with the project."
- "They decided to postpone the wedding."
- "The instructions were easy to follow."
Answers: 1. "To win the championship" — noun (subject). 2. "to buy groceries" — adverb (purpose). 3. "to help with the project" — adjective (modifies "partner"). 4. "to postpone the wedding" — noun (direct object). 5. "to follow" — adverb (modifies "easy").
Key Takeaway: Infinitive phrases are the most versatile verbal construction in English, capable of functioning as nouns, adjectives, or adverbs. Understanding their three functions, knowing which verbs take infinitives, and recognizing common patterns will help you write more varied and precise sentences.