1. Phrases & Clause Unit
The infinitive phrase

2. Acting as a noun, adjective, or adverb?
 To be or not to be, that is the question.
You have the right to remain silent.
We read to know that we are not alone.

3. Recognizing an infinitive when you see one
An infinitive will almost always begin with to followed by the simple form of the verb, to + verb = infinitive
To sneeze, to smash, to cry, to shriek, to jump, to dunk, to read, to eat, to slurp - all of these are infinitives.
Important Note: Because an infinitive is not a verb, you cannot add s, es, ed, or ing to the end. Ever!

4. Infinitive as a noun (subject, direct object, predicate nominative, etc.)
To sleep is the only thing Eli wants after his double shift waiting tables at the neighborhood café.
To sleep functions as a noun because it is the subject of the sentence.
Emanuel turned his head and refused to look.
To look functions as a noun because it is the direct object for the verb refuses.
Her goal is to play basketball for Penn State.
To play basketball for Penn State functions as a noun because it is a predicate nominative following the state of being verb is.

5. Infinitive as an adjective (which one? - what kind? - how many?)
Wherever Melissa goes, she always brings a book to read in case conversation lags or she has a long wait.
To read functions as an adjective because it modifies book.
The team's desire to win is very strong.
To win functions as an adjective because it modifies desire.
Jen's eagerness to learn is very evident.
To learn functions as an adjective because it modifies eagerness.

6. Infinitive as an adverb (usually answer why or modify a predicate adjective)
Richard braved the icy rain to get to work on time.
to get to work on time functions as an adverb because it explains why Richard braved the inclement weather.
Melvin is taking Advanced Composition this semester to improve his writing skills.
to improve his writing skills functions as an adverb because it explains why Melvin is taking the class.
The players were ready to train.
to train functions as an adverb because it modifies the predicate adjective ready.

7. Practice – infinitive functioning as a noun, adjective, or adverb & why
1. Everyone wants to enjoy life. 2. The inspector came to check the dam for leaks 3. Your idea to spend the day together sounds great. 4. Two bad habits are to smoke cigarettes and to drink alcohol. 5. This must be the best route to take. 6. To cheat is a sign of weakness. 7. The patient was unable to sleep. 8. Joe is the man to see about the job.

8. Practice – infinitive functioning as a noun, adjective, or adverb & why
Everyone wants to enjoy life.
Noun – direct object of the verb wants
The inspector came to check the dam for leaks.
Adverb – explains why the inspector came
Your idea to spend the day together sounds great.
Adjective – modifies the noun idea
Two bad habits are to smoke cigarettes and to drink alcohol.
Noun – predicate nominative following the verb is

9. Practice – infinitive functioning as a noun, adjective, or adverb & why
This must be the best route to take.
Adjective – modifies the noun route
6. To cheat is a sign of weakness.
Noun – subject of the sentence
The patient was unable to sleep.
Adverb – modifies the predicate adjective ready
Joe is the man to see about the job.
Adjective – modifies the noun man

10. Subject of an infinitive
While the word subject in grammar normally applies to a sentence, it is possible for an infinitive to have a subject.
When an infinitive or an infinitive phrase follows certain verbs, the action of the infinitive may be performed by a different person or thing than the subject of the sentence.
This doer of the infinitive's action follows the verb and comes before the infinitive.
Keep in mind that when an infinitive follows a verb, sometimes the word to is dropped from the infinitive.

11. examples We wanted Bill to go to the airport.
Simon helped me to record the data.
Dan asked Joy to take the package to the airport.
No one saw the prisoner escape.
Simon helped me record the data (In the last two examples, the word to has been dropped.)

12. To split or not to split?
The general rule is that no word should separate the to of an infinitive from the simple form of the verb that follows. If a word does come between these two components, a split infinitive results.
Examples:
I like to on a nice day walk in the woods. (unacceptable) On a nice day, I like to walk in the woods. (revised)
I needed to quickly gather my personal possessions. (acceptable in informal contexts) I needed to gather my personal possessions quickly. (revised for formal contexts)