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What Is a Split Infinitive?
A split infinitive occurs when a word (usually an adverb) is placed between "to" and the verb in an infinitive phrase. The infinitive is the base form of a verb preceded by "to": to run, to speak, to understand. A split infinitive inserts a word between these two elements:
- "To boldly go" (split) vs. "To go boldly" (unsplit)
- "To really understand" (split) vs. "To understand really" or "Really to understand" (unsplit)
- "To better serve our customers" (split) vs. "To serve our customers better" (unsplit)
The "rule" against split infinitives has been one of the most widely taught—and most widely debated—grammar prescriptions in English for over 150 years. But is it really a rule? As we will see, the answer is more nuanced than most grammar textbooks suggest.
The Most Famous Split Infinitive
The most famous split infinitive in the English language comes from the opening of Star Trek: "To boldly go where no man has gone before." This phrase, first heard in 1966, brought the split infinitive debate into popular consciousness.
Consider the alternatives:
- "Boldly to go where no man has gone before" — sounds stiff and archaic.
- "To go boldly where no man has gone before" — loses the rhythmic punch.
- "To boldly go where no man has gone before" — natural, emphatic, memorable.
The split version works best because it places the emphasis on "boldly" in a way that neither alternative achieves. The adverb sits right next to the verb it modifies, creating a tight, punchy phrase. This example illustrates the central argument in favor of split infinitives: sometimes splitting produces clearer, more natural, more emphatic prose.
History of the "Rule"
The prohibition against split infinitives first appeared in the 19th century. The earliest known explicit criticism came from an anonymous writer in 1834 who called split infinitives "objectionable." Henry Alford, the Dean of Canterbury, reinforced the prohibition in his influential The Queen's English (1864), calling the split infinitive "a practice entirely unknown to English speakers and writers" before the 14th century (a claim that has since been disproven).
The supposed rule gained traction through grammar textbooks and style guides throughout the late 19th and 20th centuries. Generations of students were taught that splitting an infinitive was a grammatical error on par with subject-verb disagreement or dangling modifiers.
However, the historical record tells a different story. Split infinitives have appeared in English writing since at least the 13th century. They appear in the works of respected writers including John Wycliffe (14th century), Samuel Johnson (18th century), Benjamin Franklin, Abraham Lincoln, George Bernard Shaw, and countless others. If it was ever truly a rule, the finest writers in English never followed it.
The Latin Connection
The origin of the split infinitive "rule" lies in the 18th and 19th century tendency to model English grammar on Latin grammar. In Latin, an infinitive is a single word (amare = "to love"), so it cannot be split. Prescriptive grammarians reasoned that since Latin infinitives cannot be split, English infinitives should not be split either.
The flaw in this reasoning is fundamental: English is not Latin. English infinitives consist of two words ("to" + verb), and English grammar follows its own rules. Applying Latin grammar to English is like applying French cooking rules to Japanese cuisine—the result may be interesting but it is not necessarily appropriate.
This same Latin-based reasoning produced other English grammar "rules" that are now widely considered myths, such as the prohibition against ending a sentence with a preposition and the prohibition against beginning a sentence with a conjunction. Understanding how English grammar actually works is more valuable than memorizing arbitrary rules inherited from another language.
The Modern View
The overwhelming consensus among modern linguists, grammarians, and style authorities is that split infinitives are grammatically acceptable in English. They are a natural feature of the language, not an error.
Here is what respected authorities say:
"The English-speaking world may be divided into (1) those who neither know nor care what a split infinitive is; (2) those who do not know, but care very much; (3) those who know and condemn; (4) those who know and approve; and (5) those who know and distinguish. Those who neither know nor care are the vast majority." — H.W. Fowler, A Dictionary of Modern English Usage (1926)
Even in 1926, Fowler recognized that the prohibition was more a matter of social convention than grammatical necessity. Nearly a century later, the consensus has shifted further: most modern grammarians fall into category (5)—they know what split infinitives are and make case-by-case decisions based on clarity and style.
When Splitting Improves Clarity
There are situations where splitting the infinitive produces a clearly superior sentence.
When the Adverb Modifies Only the Infinitive Verb
"She decided to gradually increase the dosage" is clearer than "She decided to increase the dosage gradually" (which could mean the decision was gradual) or "She decided gradually to increase the dosage" (which definitely means the decision was gradual). The split version unambiguously shows that "gradually" modifies "increase."
When Avoiding the Split Creates Ambiguity
"He failed to completely understand the problem." Without the split: "He failed to understand the problem completely" — does "completely" modify "understand" or "failed"? "He failed completely to understand the problem" — now "completely" seems to modify "failed." The split version is the only unambiguous option.
When the Split Sounds More Natural
"We expect the population to more than double by 2050." This is a natural, easily understood sentence. "We expect the population more than to double" is awkward, and "We expect the population to double by more than" changes the meaning. The split infinitive is the best option.
When Emphasis Is Important
"I want you to really listen to me." The adverb "really" between "to" and "listen" creates emphasis that would be lost in "I want you to listen to me really" or "I really want you to listen to me" (which shifts the emphasis to "want").
When to Avoid Splitting
While split infinitives are grammatically acceptable, there are situations where avoiding them produces better writing.
When Multiple Words Split the Infinitive
"She wanted to slowly and carefully and thoroughly examine every piece of evidence" is cumbersome. Moving the adverbs after the verb is cleaner: "She wanted to examine every piece of evidence slowly, carefully, and thoroughly."
When the Unsplit Version Is Equally Clear
If you can rearrange the sentence without losing clarity or creating awkwardness, there is no reason to split: "He promised to never lie" and "He promised never to lie" are equally clear and natural. Choose whichever sounds better to your ear.
When Writing for Traditionalist Audiences
Some readers—particularly in formal academic and legal contexts—still view split infinitives negatively. If you know your audience includes people who object to split infinitives, and unsplitting does not harm your sentence, it may be diplomatically wise to avoid the split. However, never sacrifice clarity to avoid a split infinitive.
What Style Guides Say
The Chicago Manual of Style (18th edition): "The split infinitive is not a grammatical error. It does tend to produce a clumsy sentence, though, and is best avoided when a natural-sounding alternative exists."
The AP Stylebook: Accepts split infinitives when avoiding them would create awkwardness or ambiguity.
Strunk and White's The Elements of Style: Does not list split infinitives among errors to avoid—a notable omission given the book's prescriptive reputation.
Garner's Modern English Usage: Classifies the prohibition against split infinitives as a "superstition" and advises writers to split infinitives freely when doing so improves the sentence.
The Oxford Guide to English Grammar: States that split infinitives are "a normal part of English" and that the old prohibition "should be ignored."
The consensus is clear: split when clarity or naturalness demands it; don't split when unsplitting produces an equally good sentence. For more on how grammar rules shape writing, see our sentence structure guide.
The Awkwardness of Avoidance
Sometimes, stubbornly avoiding a split infinitive produces a worse sentence than the split would have. These awkward avoidances are often called "contortions" or "gymnastics":
- Awkward avoidance: "The committee voted unanimously to, if necessary, table the motion." → Better split: "The committee voted to unanimously table the motion if necessary."
- Awkward avoidance: "She wanted sincerely to apologize." → Better split: "She wanted to sincerely apologize."
- Awkward avoidance: "He asked her quietly to close the door." → Does he ask quietly, or should she close quietly? Better split: "He asked her to quietly close the door" (unambiguous: she should close quietly).
As George Bernard Shaw reportedly wrote to a newspaper editor: "Every good literary craftsman splits his infinitives when the sense demands it. I call for the immediate dismissal of the man who revised my text."
Other Grammar Myths
The split infinitive prohibition belongs to a family of grammar "rules" that are more myth than reality:
"Never end a sentence with a preposition." This is another Latin-based rule that does not reflect how English actually works. "What are you looking at?" is perfectly natural. "At what are you looking?" is stilted and awkward. Winston Churchill allegedly mocked this rule: "This is the sort of English up with which I will not put."
"Never begin a sentence with 'and' or 'but.'" Respected writers have started sentences with conjunctions throughout the history of English. The Bible's King James Version begins sentences with "And" hundreds of times. Using "And" or "But" at the start of a sentence can create emphasis and improve flow.
"Never use the passive voice." The passive voice has legitimate uses—when the actor is unknown, unimportant, or obvious, or when you want to emphasize the action over the actor. "The report was completed on time" is perfectly appropriate when the writer's identity does not matter. The real advice is: prefer active voice when both options are equally clear, but use passive voice when it serves your purpose. See our guide on clear writing for more.
These "rules" share a common origin: prescriptive grammarians of the 18th and 19th centuries who tried to impose Latin-based logic on a Germanic language. While they meant well, many of their prescriptions do not reflect how English is actually used by skilled writers and speakers. For a broader view of grammar debates, see our article on double negatives.
Practical Guidelines
Here is a practical approach to split infinitives that will serve you well in any writing context:
- Prioritize clarity. If splitting the infinitive makes your meaning clearer, split it without hesitation.
- Prioritize naturalness. If the split version sounds more natural, use it. If the unsplit version sounds equally natural, use that.
- Avoid multi-word splits. Inserting one adverb between "to" and the verb is fine. Inserting three or four words is usually clumsy.
- Know your audience. In casual writing, split freely. In formal writing for traditionalist audiences, split only when necessary for clarity.
- Never sacrifice meaning to avoid a split. If unsplitting creates ambiguity or changes the meaning, the split version is the right choice.
- Read your sentence aloud. Your ear is often the best judge of whether a split infinitive sounds natural or awkward.
Conclusion
The split infinitive is not an error. It is a natural construction in English that has been used by skilled writers for over seven centuries. The prohibition against it arose from a misguided attempt to impose Latin grammar on English and has been rejected by modern grammarians, linguists, and style authorities. When a split infinitive makes your sentence clearer, more natural, or more emphatic, use it confidently. When it does not, rearrange as you see fit. The goal of writing is always communication, and any "rule" that hinders communication is not a rule worth following. To boldly write—that is the only rule that truly matters.