Recognize an infinitive when you see one.
To sneeze, to smash, to cry, to shriek, to jump, to dunk, to read, to eat, to slurp—all of these are infinitives. An infinitive will almost always begin with to followed by the simple form of the verb, like this:
To + Verb = Infinitive
Important Note: Because an infinitive is not a verb, you cannot add s, es, ed, or ing to the end. Ever!
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.
No matter how fascinating the biology dissection is, Emanuel turns his head and refuses to look.
To look functions as a noun because it is the direct object for the verb refuses.
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.
Richard braved the icy rain to throw the smelly squid eyeball stew into the apartment dumpster.
To throw functions as an adverb because it explains why Richard braved the inclement weather.
Recognize an infinitive even when it is missing the to.
An infinitive will almost always begin with to. Exceptions do occur, however. An infinitive will lose its to when it follows certain verbs. These verbs are feel, hear, help, let, make, see, and watch.
The pattern looks like this:
Special Verb + Direct Object + Infinitive - to
Here are some examples:
As soon as Theodore felt the rain splatter on his hot, dusty skin, he knew that he had a good excuse to return the lawn mower to the garage.
Felt = special verb; rain = direct object; splatter = infinitive minus the to.
When Danny heard the alarm clock buzz, he slapped the snooze button and burrowed under the covers for ten more minutes of sleep.
Heard = special verb; alarm clock = direct object; buzz = infinitive minus the to.
Although Dr. Ribley spent an extra class period helping us understand logarithms, we still bombed the test.
Helping = special verb; us = direct object; understand = infinitive minus the to.
Because Freddie had never touched a snake, I removed the cover of the cage and let him pet Squeeze, my seven-foot python.
Let = special verb; him = direct object; pet = infinitive minus the to.
Since Jose had destroyed Sylvia's spotless kitchen while baking chocolate-broccoli muffins, she made him take her out for an expensive dinner.
Made = special verb; him = direct object; take = infinitive minus the to.
I said a prayer when I saw my friends mount the Kumba, a frightening roller coaster that twists and rolls like a giant sea serpent.
Saw = special verb; my friends = direct object; mount = infinitive minus the to.
Hoping to lose her fear of flying, Rachel went to the airport to watch passenger planes take off and land, but even this exercise did not convince her that jets were safe.
Watch = special verb; passenger planes = direct object; take, land = infinitives minus the to.
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. Look at the example that follows:
Wrong: Sara hopes to quickly finish her chemistry homework so that she can return to the more interesting Stephen King novel she had to abandon. Right: Sara hopes to finish her chemistry homework quickly so that she can return to the more interesting Stephen King novel she had to abandon.
Some English teachers believe that thou shall not split infinitives was written on the stone tablets that Moses carried down from the mountain. Breaking the rule, in their eyes, is equivalent to killing, stealing, coveting another man's wife, or dishonoring one's parents. If you have this type of English teacher, then don't split infinitives!
Other folks, however, consider the split infinitive a construction, not an error. They believe that split infinitives are perfectly appropriate, especially in informal writing.
In fact, an infinitive will occasionally require splitting, sometimes for meaning and sometimes for sentence cadence. One of the most celebrated split infinitives begins every episode of Star Trek: "To boldly go where no one has gone before ...." Boldly to go? To go boldly? Neither option is as effective as the original!
When you are making the decision to split or not to split, consider your audience. If the piece of writing is very formal and you can maneuver the words to avoid splitting the infinitive, then do so. If you like the infinitive split and know that its presence will not hurt the effectiveness of your writing, leave it alone.