Infinitive Phrase (Types of Infinitives & Examples)

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What Is an Infinitive Phrase?

An infinitive phrase is a group of words structured around an infinitive (to + base verb) that contains any associated objects, complements, or modifiers connected with it.

These phrases make sentences more informative without requiring an additional full clause, expressing an action, purpose, intention, description, or result in a compact grammatical form.

Infinitive Phrases in Different Sentence Roles

Notice how infinitive phrases perform completely different grammatical jobs depending on context:

To learn a new language takes time. Noun Function (Subject)
She wants to learn a new language. Noun Function (Direct Object)
He needs a book to learn from. Adjectival Function (Modifies book)
She joined the course to improve her writing. Adverbial Function (Expresses Purpose)

Understanding infinitive phrases involves more than just spotting to + verb; you must also analyze what follows the infinitive and determine the syntactic role of the complete unit.

Common Pattern of an Infinitive Phrase

Formula: to + base verb + objects / complements / modifiers
Example Breakdown: “to read a book quietly”
  • Infinitive: to read
  • Object of the Infinitive: a book
  • Adverb Modifying the Infinitive: quietly
➔ Complete Infinitive Phrase: to read a book quietly

An infinitive phrase can function as a noun, an adjective, or an adverb.

Infinitive vs. Infinitive Phrase

A bare infinitive consists solely of two words (to + base verb). When additional objects, complements, or modifiers are attached, the entire group expands into an infinitive phrase.

Bare Infinitive: to swim
Expanded Infinitive Phrase: to swim across the river
Bare Infinitive Expanded Infinitive Phrase
to read to read the book
to sing to sing beautifully
to solve to solve the difficult problem
to travel to travel around the world
to help to help my younger brother

Quick Challenge

Three of these four options contain an infinitive phrase. One contains a prepositional phrase instead. Tap the one that doesn’t belong.

See the full answer

Answer: “to the train station”

An infinitive phrase always requires the structure to + base verb (e.g., to solve, to travel, to read). In “to the train station,” the word to is a preposition followed by a noun phrase (the train station), creating a prepositional phrase rather than an infinitive phrase.

Types of Infinitives

English verbs form two main types of infinitives: full infinitives (with to) and bare infinitives (without to).

1. Full Infinitives (to-Infinitives)

Formed with the particle to + base verb:

to write to understand to leave to improve

Full infinitives are widely used in sentences across nominal, adjectival, and adverbial roles:

  • She hopes to win the competition.
  • He went outside to get some fresh air.
  • I need a chair to sit on.
2. Bare Infinitives (Zero Infinitives)

The base form of the verb used without the marker to (e.g., go, eat, write, leave). Bare infinitives appear in three specific grammatical environments:

• After Modal Auxiliaries (must, can, could, might, should, will, would):
“You must leave now.” / “She can swim well.” / “They might arrive late.” / “We should wait here.”
• After Perception Verbs (see, hear, feel, watch, notice) when describing complete actions:
“I saw him cross the road.” / “We heard the baby cry.” / “She watched the children play.”
• After Causative Verbs Let and Make:
“Let me help you.” / “The teacher made us rewrite the paragraph.”
Is Every Bare Infinitive an Infinitive Phrase?

While broader grammatical analysis includes bare-infinitive structures as non-finite phrases, practical language analysis focuses primarily on full to-infinitive phrases.

What Can an Infinitive Phrase Contain?

Because infinitives are derived from verbs, they can take their own objects, complements, and modifiers while remaining a unified non-finite phrase:

Internal Element Example Infinitive Phrase
Infinitive core to read
Direct object to read the book
Indirect object + Direct object to give her a gift
Adverb modifier to speak quietly
Prepositional phrase modifier to work in the office
Multiple combined elements to finish the project before Friday

What Are the Functions of Infinitive Phrases?

An infinitive phrase can perform three major syntactic functions: Noun, Adjective, or Adverb.

• Noun Function (Subject): “To exercise regularly is healthy.” (Names the activity)
• Noun Function (Direct Object): “I like to exercise regularly.” (Receives the action of like)
• Adverbial Function (Purpose): “She wakes up early to exercise regularly.” (Explains why she wakes up early)

Infinitive Phrases as Nouns: Subject Position

When an infinitive phrase acts as a noun, it can occupy the subject position of a clause:

  • “To travel alone can be exciting.” ➔ Subject of the predicate can be exciting.
  • “To learn from mistakes is important.” ➔ Subject of the linking verb is.
Subject Identification Test:

Ask: What is the sentence asserting something about?
• In “To save money requires discipline,” ask: What requires discipline? ➔ To save money.

This confirms that the infinitive phrase operates as the Subject of the verb requires.
Key Takeaway:

Whether an infinitive appears in its full form (to-infinitive) or bare form (after modals, perception verbs, or let/make), it can govern objects and modifiers to function as a noun, adjective, or adverb.

Infinitive Phrase as a Direct Object

An infinitive phrase can follow transitive verbs to receive the action as a direct object, answering the question “What?”:

  • “She wants to study medicine.”
    ➔ What does she want? To study medicine.
  • “They decided to postpone the meeting.”
    ➔ What did they decide? To postpone the meeting.

Common Verbs Followed by Infinitives

Many English verbs pair specifically with full to-infinitives when taking non-finite objects:

agree choose decide expect hope learn manage need offer plan prepare promise refuse seem try want wish
  • We plan to visit the museum.
  • She refused to answer the question.
  • He promised to help us.

Infinitive Phrase as a Subject Complement

Following a linking verb (such as is, was, became), an infinitive phrase can identify, rename, or define the subject:

• “Her dream is to become a doctor.” (Defines Her dream)
• “My main goal is to improve my writing.” (Defines My main goal)
Subject Infinitive Phrase Syntactic Function
Her goal to win Subject complement
My plan to study abroad Subject complement
Their aim to reduce costs Subject complement

Infinitive Phrases as Adjectives

An infinitive phrase functions adjectivally when it postmodifies a noun or pronoun, describing its purpose, nature, or intended use:

“I need a book to read.”

Which book? A book to read. The infinitive phrase describes and identifies the noun book.

  • She needs someone to help her. (Modifies pronoun someone)
  • We have several problems to solve. (Modifies noun problems)
  • He brought some food to share. (Modifies noun food)
  • There is no place to sit. (Modifies noun place)
How to Recognize an Adjectival Infinitive Phrase:
Which one? What kind? What is its intended use?

Example: “I need a chair to sit on.”
➔ Which chair? The chair to sit on. The phrase modifies chair.

Adjectival Infinitive Phrase Examples

Sentence Infinitive Phrase Word Modified
I have work to finish. to finish work
She needs a friend to talk to. to talk to friend
We found a place to stay. to stay place
He has several questions to ask. to ask questions
They need a machine to cut the wood. to cut the wood machine

Infinitive Phrases as Adverbs

An infinitive phrase functions adverbially when it modifies a verb by explaining the purpose, reason, or result of the action.

1. Expressing Purpose (The “In Order To” Test)

Answering “Why did the action happen?” is the most common adverbial role:

  • “He saved money to buy a car.”
  • “She called me to ask a question.”
  • “They arrived early to get good seats.”
  • “I joined the course to improve my English.”
Purpose infinitives can be tested by substituting “in order to”:
“She went outside to get some fresh air.” ≈ “She went outside in order to get some fresh air.”

2. Expressing Result or Consequence

In specific constructions, an infinitive phrase indicates an outcome rather than an intentional purpose:

  • “He lived to see his grandchildren grow up.”
  • “She worked hard to become one of the company’s best employees.”

3. Fronted Infinitive Phrases

When an adverbial infinitive of purpose opens a sentence, it is followed by a comma to separate the introductory modifier from the main clause:

  • To save time, we took a taxi.
  • To avoid confusion, label each file clearly.
Key Takeaway:

Infinitive phrases adapt smoothly across clause environments: functioning as noun objects or complements after specific verbs, as adjectives describing nouns, or as adverbs explaining purpose and outcome.

Quick Challenge

Three of these sentences use an infinitive phrase functioning as an adverb of purpose. One functions as an adjective modifying a noun. Tap the one that doesn’t belong.

See the full answer

Answer: “I need a quiet book to read.”

In the sentences “He saved money to buy a car,” “They arrived early to get good seats,” and “To save time, we took a taxi,” the infinitive phrases function adverbially by explaining why the actions took place (purpose test: in order to).

In contrast, in “I need a quiet book to read,” the infinitive phrase to read functions adjectivally to describe and identify the noun book.

How to Identify an Infinitive Phrase

Follow this 4-step diagnostic method to locate and classify infinitive phrases accurately:

Step 1: Look for an Infinitive (to + Base Verb)
Scan the sentence for the infinitive marker to followed directly by a base verb:
to read to write to understand to improve to travel
Caution: Verify that to is not functioning as a preposition governing a noun object.
Step 2: Gather All Connected Objects and Modifiers
Do not stop at to + verb if subsequent words attach to the action:
• In “She wants to read the entire book before Friday,” the complete infinitive phrase is to read the entire book before Friday.
Step 3: Determine the Phrase’s Functional Job
• Noun: “To exercise every morning is healthy.” ➔ Acts as the subject.
• Adjective: “I need a place to study.” ➔ Modifies the noun place.
• Adverb: “She went to the gym to exercise.” ➔ Explains why she went (Purpose).
Step 4: Identify the Exact Target Word It Relates To
• “The student decided to study harder.” ➔ Connected to verb decided (Direct object).
• “The student found a quiet place to study.” ➔ Modifies noun place (Adjective).
• “To study harder requires discipline.” ➔ Functions independently as the clause Subject.

Infinitive Phrase Examples by Function

Sentence Infinitive Phrase Function
To read widely improves vocabulary. To read widely Noun (Subject)
She wants to read widely. to read widely Noun (Direct object)
Her aim is to read more books. to read more books Subject complement
I need a book to read. to read Adjective
He went to the library to study. to study Adverb (Purpose)
She bought a notebook to record her ideas. to record her ideas Adjective
To finish on time was difficult. To finish on time Noun (Subject)
They worked late to finish the report. to finish the report Adverb (Purpose)

Infinitive Phrase vs. Prepositional Phrase

The word to can function either as an infinitive particle or as a preposition:

Prepositional Phrase (to + Noun/Pronoun Object):
“We went to the park.”
To is followed by the noun phrase the park.
Infinitive Phrase (to + Base Verb):
“We wanted to play.”
To is followed directly by the base verb play.
Example Role of “to” Construction Type
to the park Preposition Prepositional phrase
to school Preposition Prepositional phrase
to read Infinitive marker Infinitive
to study English Infinitive marker Infinitive phrase
to the teacher Preposition Prepositional phrase
to help my friend Infinitive marker Infinitive phrase
Quick Structural Test:
  • to + noun / pronoun ➔ Prepositional Phrase (e.g., “She walked to the office.”)
  • to + base verb ➔ Infinitive Phrase (e.g., “She went there to work.”)

Infinitive Phrase vs. Gerund Phrase

Both infinitives and gerunds (-ing forms) express actions and can function as subjects (“To swim is enjoyable” vs. “Swimming is enjoyable”). However, specific verbs and prepositions require one over the other:

• Infinitive verb selection: “I decided to leave.” (The verb decide takes an infinitive)
• Gerund verb selection: “I enjoy reading.” (The verb enjoy takes a gerund)
• After prepositions: “She is interested in learning English.” (Never in to learn)
Infinitive Form Gerund Form
to readreading
to swimswimming
to studystudying
to writewriting
to traveltraveling

Infinitive Phrase vs. Verb Phrase

An infinitive originates from a verb, but an infinitive phrase does not serve as the main finite predicate of the clause:

Finite Verb Phrase (Expresses tense, person, predicate):
“She is studying English.” ➔ Predicate
Non-Finite Infinitive Phrase (Acts nominally as direct object):
“She wants to study English.” ➔ Object of wants

The infinitive takes objects and modifiers like a verb, but it lacks tense markings and subject-verb agreement.

Infinitive Phrases with an Stated Actor / Performer

When the performer of the infinitive differs from the subject of the main clause, the actor is placed directly before the infinitive in the objective case:

Subject as Actor:
“I want to finish the work.”
(Understood performer of finish is I)
Separate Stated Actor:
“I want you to finish the work.”
• Main subject: I
• Main verb: want
• Stated actor: you
• Infinitive phrase: to finish the work

Verbs that commonly license this pattern include:

ask advise allow encourage expect force invite remind tell want need

Infinitive Phrases After Adjectives

Infinitives frequently follow predicate adjectives as complements, providing essential context about an emotion, evaluation, judgment, or level of difficulty:

  • “I am happy to help.” (Emotion / Willingness)
  • “She was surprised to see him.” (Reaction)
  • “This problem is difficult to solve.” (Evaluation / Challenge)
  • “The instructions are easy to follow.” (Clarity / Accessibility)

Common Adjective + Infinitive Patterns

Structural Pattern Example Construction
adjective + infinitive happy to help
adjective + infinitive phrase difficult to understand the instructions
too + adjective + infinitive too tired to work
adjective + enough + infinitive strong enough to lift it

Infinitive Phrases with “Too” and “Enough”

In degree constructions, the infinitive phrase completes the adjective by expressing sufficiency or limitation:

Too + Adjective + Infinitive (Negative Consequence / Limitation):
“The box is too heavy to lift.” / “She was too tired to continue.”
Explains the resulting impossibility due to excessive degree.
Adjective + Enough + Infinitive (Sufficiency / Capability):
“He is strong enough to carry the box.” / “The room is large enough to hold everyone.”
Establishes that the quality meets the threshold required for the action.

Infinitive Phrases for Purpose

An infinitive phrase answers the question “Why?”, functioning adverbially to state intention or purpose:

  • “She went to the market to buy vegetables.”
  • “He studied hard to pass the examination.” (Why did he study hard? ➔ To pass the examination)
  • “We left early to avoid traffic.”
• Purpose Infinitive Phrase: “He studied hard to pass the examination.” (Non-finite, concise)
• Purpose Subordinate Clause: “He studied hard so that he could pass the examination.” (Finite clause with subject + modal verb)

Split Infinitives: Modern Usage & Practical Rules

A split infinitive occurs when an intervening word (typically an adverb) is placed between the marker to and the base verb:

to carefully examine to fully understand to completely remove
Is Splitting an Infinitive an Error?

Modern English usage does not treat split infinitives as errors. While traditional prescriptivism discouraged them, placing the adverb inside the infinitive is often the most natural, unambiguous choice:

• “She decided to carefully examine the evidence.” (Split – clear adverb attachment)
• “She decided to examine the evidence carefully.” (Unsplit – natural alternative)
Rule: In “They need to carefully review the documents,” the split placement confirms that carefully modifies review rather than need. Choose whichever position offers maximum clarity and rhythmic flow.

Aspectual and Voice Forms of Infinitive Phrases

1. Passive Infinitive Phrases (to + be + past participle)

Focuses on the recipient or object of the non-finite action:

to be invited to be selected to be completed to be repaired
  • She hopes to be selected for the team.
  • The work needs to be completed by Friday.
  • He expected to be invited to the meeting.
2. Continuous Infinitive Phrases (to + be + -ing form)

Emphasizes that the action is ongoing, in progress, or simultaneous:

to be working to be waiting to be studying
  • She seems to be waiting for someone.
  • I would like to be traveling during the summer.
  • He appears to be working on a new project.
3. Perfect Infinitive Phrases (to + have + past participle)

Refers to an action completed prior to the time frame of the main verb:

to have finished to have forgotten to have seen
  • She seems to have forgotten the appointment. (Forgot prior to seeming)
  • He claims to have completed the work.
  • They were lucky to have found a solution.

How Infinitive Phrases Can Be Nested

An infinitive phrase can serve as the direct object or complement of another infinitive, creating layered, non-finite hierarchies:

“She wants to learn to play the piano.”
• Primary Infinitive Phrase: to learn to play the piano (Object of wants)
• Nested Infinitive Phrase: to play the piano (Object of learn)
Another example:
“He decided to try to solve the problem.”
Contains two cascading infinitives: to try governing to solve.

While nested infinitives are grammatically valid, stacking three or more in a single sentence can create processing fatigue for readers.

Infinitive Phrases and Punctuation

Punctuation with infinitive phrases depends entirely on whether the phrase appears in an introductory, medial, or final sentence position:

1. Introductory Phrase (Comma Required)

When an adverbial infinitive of purpose opens the sentence, separate it with a comma:

  • To avoid delays, we left early.
  • To understand the problem, read the instructions carefully.
2. Final Position (No Comma)

Short adverbial or complement phrases at the end of a clause do not take punctuation:

“She went outside to get some air.”
3. Avoid Unnecessary Verb Splits

Never place a comma between a main verb and the infinitive completing it:

❌ Error: “She decided, to leave early.”
✅ Correct: “She decided to leave early.”

Common Mistakes with Infinitive Phrases

Mistake 1: Confusing “to” (Infinitive Marker) with a Preposition
• In “I want to study,” to is the non-finite infinitive marker, not a preposition.
• In “I went to school,” to is a preposition governing the noun object school.
Mistake 2: Truncating the Phrase Too Early

In “She wants to read the entire book tonight,” the phrase is not merely to read. The complete infinitive phrase encompasses its direct object (the entire book) and adverbial modifier (tonight).

Mistake 3: Assuming Every “to + Verb” Has the Same Syntactic Function
• “To exercise regularly is healthy.” ➔ Noun (Subject)
• “She exercises to stay healthy.” ➔ Adverb (Purpose)
Mistake 4: Using a Gerund After an Infinitive-Only Verb
• ❌ Incorrect: “I decided leaving.” ➔ ✅ Correct: “I decided to leave.”
• ❌ Incorrect: “She promised helping.” ➔ ✅ Correct: “She promised to help.”
Mistake 5: Inserting “to” After a Modal Auxiliary
Modal verbs (can, could, should, must, might, will, would) require a bare infinitive without to:
• ❌ Incorrect: “She can to swim.” ➔ ✅ Correct: “She can swim.”
• ✅ Correct: “You should study.” / “They might arrive late.” / “We must leave now.”
Mistake 6: Creating Ambiguous or Dangling Infinitive Modifiers

In “She bought a book to read on the train,” the placement clearly modifies book or explains purpose. However, placing long infinitive modifiers far from their target nouns creates ambiguity. When modifier attachment is uncertain, rephrase the sentence directly.

Infinitive Phrases in Formal and Academic Writing

In academic, scientific, and professional prose, infinitive phrases are widely used to articulate research aims, project scopes, and experimental objectives concisely without inflating clause length:

Wordy Subordinate Clause:
“The researchers conducted the experiment because they wanted to test the theory.”
Concise Infinitive of Purpose:
“The researchers conducted the experiment to test the theory.”
  • “The study was designed to examine the effects of sleep.”
  • “The researchers collected additional data to improve the accuracy of the results.”
  • “The committee met to discuss the proposed changes.”

Infinitive Phrases vs. Other Major Phrase Types

Phrases are distinguished by their structural head—the central grammatical word that anchors the construction:

Phrase Type Example Phrase Head / Main Element
Infinitive phrase to read the book infinitive (to read)
Gerund phrase reading the book gerund (reading)
Prepositional phrase in the library preposition (in)
Noun phrase the old library noun (library)
Adjective phrase very difficult adjective (difficult)
Adverbial phrase very quickly adverb (quickly)

A Quick Comparison of Infinitive Functions

The same core grammatical structure can fulfill diverse syntactic roles:

Function Example Sentence Syntactic Job
Noun To learn English takes time. Acts as the Subject
Noun She wants to learn English. Acts as the Direct Object
Complement Her goal is to learn English. Subject Complement (renames subject)
Adjective She needs a book to learn English. Modifies the noun book
Adverb She studies to learn English. Modifies verb (Expresses Purpose)

Practice Exercises

Exercise 1: Identify the Complete Infinitive Phrase
  1. I want to learn Spanish.
  2. She went to the library to study.
  3. He needs a computer to complete the project.
  4. To understand grammar takes practice.
  5. They decided to postpone the meeting.
  6. We arrived early to get good seats.
  7. She has several books to read.
  8. He hopes to become a doctor.
  9. To finish the work on time was difficult.
  10. I need someone to help me.
No. Complete Infinitive Phrase
1to learn Spanish
2to study
3to complete the project
4To understand grammar
5to postpone the meeting
6to get good seats
7to read
8to become a doctor
9To finish the work on time
10to help me
Exercise 2: Identify the Syntactic Function
  1. To exercise regularly is beneficial.
  2. She wants to exercise regularly.
  3. He went outside to exercise.
  4. I need a place to study.
  5. Their goal is to win the competition.
  6. We arrived early to find a parking space.
  7. She has several questions to ask.
  8. To speak clearly requires practice.
No. Infinitive Phrase Syntactic Function
1To exercise regularlyNoun — Subject
2to exercise regularlyNoun — Direct Object
3to exerciseAdverb — Purpose
4to studyAdjective — Modifies place
5to win the competitionNoun — Subject Complement
6to find a parking spaceAdverb — Purpose
7to askAdjective — Modifies questions
8To speak clearlyNoun — Subject
Exercise 3: Choose the Correct Form
  • She decided to leave early. (decide + infinitive)
  • He can swim very well. (Modal can + bare infinitive)
  • I enjoy reading novels. (enjoy + gerund)
  • They hope to win the match. (hope + infinitive)
  • We went to the store to buy some bread. (Infinitive of purpose)
  • She is interested in learning French. (Preposition in + gerund)
  • He made me apologize. (Causative make + bare infinitive)
  • I need someone to help me. (Adjectival infinitive modifying someone)

Frequently Asked Questions About Infinitive Phrases

What is an infinitive phrase?
An infinitive phrase is a group of words built around an infinitive (to + base verb) that includes its attached objects, complements, and modifying adverbs or prepositional phrases:
“to finish the work quickly”
Contains infinitive to finish + object the work + adverb quickly.
What is the basic structure of an infinitive phrase?
The standard formula is to + base verb + additional words (objects/modifiers), as seen in “to solve the difficult problem.”
What are the three main functions of an infinitive phrase?
An infinitive phrase can function as a Noun (subject, direct object, complement), an Adjective (modifying nominals), or an Adverb (expressing purpose, reason, or result).
Can an infinitive phrase be the subject of a sentence?
Yes. In “To exercise regularly is good for you,” the infinitive phrase operates as the grammatical subject of the linking verb is.
Can an infinitive phrase be an object?
Yes. In “She wants to learn English,” the phrase acts as the direct object answering “What does she want?”.
Can an infinitive phrase modify a noun?
Yes. When following a nominal entity, it performs an adjectival role (e.g., “I need a book to read“ modifies book).
Can an infinitive phrase express purpose?
Yes. This is its most frequent adverbial application: in “She went to the library to study,” the phrase explains why she went.
Is “to” always part of an infinitive?
No. To is an infinitive marker only when followed by a base verb (to play). When followed by a noun or pronoun (to the park), it functions as a preposition. Furthermore, bare infinitives omit to entirely after modal verbs and causatives.
What is a bare infinitive?
A bare infinitive is the base form of the verb without the particle to, used after modals (can go, must leave) and causative verbs (let him speak, made us rewrite).
What is a split infinitive?
A split infinitive occurs when an adverb is placed between to and the base verb (e.g., “to carefully examine”). In modern English, split infinitives are fully acceptable and often provide the clearest modifier attachment.
Can an infinitive phrase contain an object or an adverb?
Yes. Infinitives retain verbal properties: they can take direct objects (“to read the book“) and adverbial modifiers (“to speak clearly“).
What is the difference between an infinitive and an infinitive phrase?
An infinitive is the simple two-word core (to write), whereas an infinitive phrase includes that core plus all connected objects and modifiers (to write a detailed report carefully).
What is the difference between an infinitive phrase and a gerund phrase?
An infinitive phrase is built on to + verb (to learn English), whereas a gerund phrase is centered on an -ing noun-verb form (learning English). Both can act as subjects, but specific governing verbs and prepositions strictly mandate one form over the other.
Key Takeaway:

Infinitive phrases provide powerful syntactic flexibility across academic and everyday writing. By mastering their functional roles (noun, adjective, adverb) and structural boundaries, you ensure clear, concise, and grammatically precise sentences.

Infinitive Phrases Explained With Examples

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