1. What is an Infinitive Phrase?
An infinitive phrase is a group of words that uses an infinitive (“to” + verb). An infinitive is a verbal (a word that expresses action); so, an infinitive phrase has the same role of expressing action in a sentence.
An infinitive phrase is just a part of a sentence, working like a noun, adjective, or adverb.
Here are some examples off infinitive phrases, both on their own and as part of full sentences:
- To plant a garden
- To go on vacation
- I told the dog to run home quickly
- I want to eat pizza for dinner
The next section explains what makes infinitive phrases.
3. Parts of Infinitive Phrases
Infinitive phrases begin with an infinitive, and sometimes include modifiers and/or objects that make the phrase more descriptive.
The main, most essential part of an infinitive phrase is an infinitive. So, what’s an infinitive? Quite simply, it’s the word “to” plus the base form of a verb, like these:
- To study (to + study)
- To play (to + play)
- To leave (to + leave)
- To eat (to + eat)
Infinitives are verbal words expressing action, and shouldn’t be confused with a prepositional phrase that begins with “to” (to + noun or pronoun—see How to Avoid Mistakes).
An object is the word (a noun or a pronoun) affected by the verb in a sentence. So, in an infinitive phrase, it’s the word being affected by the infinitive. Here are some examples of objects in infinitive phrases:
- To study math
- To play guitar
- To leave the party
- To eat a sandwich
A modifier is an adjective or adverb that alters other words in a sentence, making it more descriptive. Infinitive phrases often include modifiers; here are some examples:
- To study advanced math Adjective modifying “math”
- To eat a giant sandwich Adjective modifying “sandwich”
- To play guitar beautifully Adverb modifying “to play”
- To leave the party quietly Adverb modifying “to leave”
3. Types of Infinitive Phrases
Infinitive phrases are always easy to spot because they begin with “to.” In a sentence, they can work like nouns, adjectives, or adverbs.
a. Infinitive Phrase as a Noun
When an infinitive phrase works like a noun, it answers the question “what?” So, the infinitive phrase will be the subject, which does the verb; or an object, which receives the action of the verb. Here are some examples:
- I don’t want to study for my test. What don’t you want? (Object)
- He needs to ace the exam. What does he need? (Object)
- To get good grades is my goal. What is the goal? (Subject)
- His job was to tutor me in math. What was his job? (Object)
b. Infinitive Phrase as an Adjective
When an infinitive phrase acts like an adjective in a sentence, it describes a noun or a pronoun. So, that means it will describe a subject or an object. Here are some examples:
- I want a tutor to help me study. Describes the tutor
- I need a magazine to read on the train. Describes the magazine
- There is a basket to put your exam in. Describes the basket
- I wish I had a friend to study with me. Describes the friend
c. Infinitive Phrase as an Adverb
When an infinitive phrase works like an adverb, it modifies the verb in a sentence. Adverbs answer questions like where, when, why, how, and for what reason/purpose, so, as an adverb, the infinitive will answer the same questions.
- I went home to study for math. Why did you go home?
- He sat down to take the exam. For what reason did he sit down?
- To get into college, you need good grades. Why do you need good grades?
- To ace the exam, I studied for hours. For what purpose did you study?
4. How to Avoid Mistakes
Using infinitive phrases isn’t very difficult, but, it’s important not to confuse them with prepositional phrases or try to use them as full sentences. To help avoid mistakes, you need to know these things:
a. A Phrase isn’t a Sentence
There’s one rule that is really easy to remember: an infinitive phrase can’t be a full sentence on its own. Like all phrases, it doesn’t contain the subject-verb combination that forms a clause. You can think about it like this: since a noun, adverb or adjective can’t be a full sentence, neither can an infinitive phrase. It is just a part of a sentence, and needs an independent clause to be complete.
b. Prepositional Phrases beginning with “to” are not Infinitives
A prepositional phrase expresses time and location and can sometimes begin with “to.” Even though they also use the word “to,” prepositional phrases are different then infinitives because infinitives combine “to” and a verb, while prepositional phrases combine “to” with a noun or pronoun. Look at the prepositional phrases underlined here:
- Go to bed.
- You can give that to me.
- I am going to my house.
- The letter is addressed to you.
Each of these examples is the word “to” plus a noun, not a verb. So, these are prepositional phrases, not infinitive phrases.