Summary
Infinitive verbs in English are unusual because they consist of two words – to + verb (for example, to write, to analyse, to understand). In formal academic and scientific English, these two parts traditionally stay together. Inserting a word, usually an adverb, between to and the verb creates a “split infinitive” (for example, to carefully analyse). Although split infinitives are common in everyday language, many examiners, reviewers, and journal editors still regard them as stylistically weak or even grammatically incorrect, especially in high-stakes documents such as theses, dissertations, and journal articles.
This article explains what infinitives are, why split infinitives became controversial, and how you can recognise and revise them in your own writing. It discusses when a split infinitive may be acceptable, when it is better to avoid one, and how you can preserve both grammatical correctness and natural word order without distorting your meaning. Practical examples, revision strategies, and a short checklist help you edit your drafts so that any remaining split infinitives appear deliberate rather than careless.
By understanding the structure and function of English infinitives, you can improve the precision and tone of your academic prose and present your work in a way that satisfies even conservative readers of scholarly English.
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The Correct Use of Infinitive Verbs in Academic & Scientific English
1. Why Infinitives Matter in Scholarly Writing
In academic and scientific English, very small choices in grammar and word order can influence how your writing is perceived. Examiners and journal reviewers pay close attention to clarity, precision, and control of formal style. One feature that often attracts comment is the infinitive verb and, in particular, the decision to split it or keep it intact.
Infinitives are everywhere in scholarly texts:
- to test a hypothesis
- to determine whether the method works
- to increase the reliability of the results
- to understand how the system behaves
Because they appear so frequently in aims, objectives, and explanations of method, any awkwardness in their use quickly becomes noticeable. A single split infinitive in a casual email rarely matters, but repeated split infinitives in a thesis, dissertation, or journal article can suggest inattention to detail or limited awareness of formal style conventions.
2. What an English Infinitive Is
Unlike many languages in which an infinitive is a single word (for example, Latin venire “to come”), English typically forms the infinitive with two words:
- to come
- to see
- to conquer
- to analyse
- to investigate
The particle to plus the base form of the verb together function as a single grammatical unit. In formal terms, to does not simply act as a loose preposition; it marks the infinitive form of the verb. As a result, many stylists and grammarians prefer to keep to and the verb next to each other in written English, especially in careful prose.
3. What a Split Infinitive Is
A split infinitive occurs when another word, usually an adverb or adverbial phrase, appears between to and the verb:
- to carefully analyse the data
- to successfully complete the project
- to fully understand the mechanism
In each case, the infinitive is to analyse, to complete, to understand; the adverb has been placed inside the infinitive, separating its two parts. In modern English, these constructions sound natural in conversation and informal writing, which is why they appear so often.
However, some readers still object to them in formal contexts. For those readers, the infinitive is a single unit that should remain intact, and they regard splitting it as a sign of careless or “non-standard” style.
4. Historical Attitudes to Split Infinitives
The rule against split infinitives emerged in the nineteenth century, when grammarians often tried to model English on Latin structures. Since the Latin infinitive is a single word, some commentators concluded that English infinitives should also remain “unsplit.” This reasoning is not linguistically necessary, but it has influenced style advice for well over a century.
Today, usage guides are more divided. Many modern handbooks accept that a split infinitive is not a grammatical error in a strict sense, especially when moving the adverb would make the sentence ambiguous or unnatural. Nonetheless, several conservative style guides—and many examiners—still view frequent split infinitives as stylistically weak in formal writing.
For students and researchers, the safest approach is pragmatic: understand that some readers dislike them, minimise their use in serious academic work, and retain one only when every alternative is clearly worse.
5. Problems Split Infinitives Can Cause
Split infinitives can create several issues in scholarly prose:
5.1 Perception of Informality
Because split infinitives are very common in speech and casual writing, they can make a formal text sound conversational. A sentence such as “The aim of this study is to rigorously test the following hypotheses” may appear less polished than “The aim of this study is to test the following hypotheses rigorously.”
5.2 Potential Ambiguity
Sometimes the position of the adverb affects the meaning of the sentence. Consider the difference between:
- to nearly double the sample size
- to double the sample size nearly
The first phrase usually means that the increase fell slightly short of a full doubling; the second phrase is awkward and unclear. In such cases, a split infinitive may actually convey the meaning more precisely, which is why many modern style guides now accept this construction.
5.3 Rhythm and Readability
In other cases, a split infinitive disrupts the rhythm of a sentence or places too much emphasis on a minor adverb. Moving the adverb away from the infinitive can smooth the sentence and help important information stand out in a more logical place.
6. How to Recognise and Revise Split Infinitives
The easiest way to manage split infinitives in your writing is to include them in your editing and proofreading routine. When you read through a draft, look for the pattern:
- to + adverb / adverbial phrase + verb
Examples:
- to strongly suggest
- to thoroughly investigate
- to clearly demonstrate
Once you detect such a phrase, consider one of the following revision strategies.
6.1 Move the Adverb After the Verb
Often, the simplest fix is to move the adverb to a position after the infinitive:
- Original: The study aims to systematically assess the intervention.
- Revised: The study aims to assess the intervention systematically.
This adjustment keeps the infinitive intact and preserves the meaning.
6.2 Move the Adverb Before the Infinitive
Sometimes it is better to place the adverb before to:
- Original: Our objective is to comprehensively review the literature.
- Revised: Our objective is comprehensively to review the literature.
This solution appears more traditional and can sound slightly formal. It is grammatically correct, but in some sentences it may feel heavy. Use it sparingly and only when it reads naturally in context.
6.3 Rewrite the Sentence
In more complex sentences, shifting a single adverb may not solve the problem elegantly. In such cases, consider rewording the entire clause:
- Original: The project seeks to significantly improve access to healthcare.
- Revised: The project seeks a significant improvement in access to healthcare.
Here, a change in structure removes the infinitive altogether and produces a more concise phrase.
7. When a Split Infinitive May Be Justified
Although it is wise to minimise split infinitives in academic and scientific writing, there are cases in which keeping one may be the best option:
- when moving the adverb creates ambiguity;
- when every alternative sounds clumsy or changes the emphasis in an unhelpful way;
- when a particular phrase has become established and widely accepted (for example, in a fixed expression or quotation).
In these situations, you can decide to retain the split infinitive deliberately. If you do so, make sure that the rest of your writing displays strong control of formal style, so that readers understand the choice as intentional rather than careless.
8. Practical Guidelines for Academic Writers
When you prepare a thesis, dissertation, journal article, or research report, the following guidelines can help you manage infinitives effectively:
-
Learn to recognise infinitives and split infinitives.
During proofreading, highlight every instance of to + verb. Check whether any adverbs sit between the two, and decide case by case whether they can move. -
Prefer unsplit infinitives in formal sections.
In aims, hypotheses, methods, and conclusions, maintain a more conservative style. These sections are often examined most closely. -
Revise where a simple change improves style.
If you can move the adverb after the verb without harming the sentence, do so. This change usually improves the flow and eliminates potential objections. -
Reword awkward sentences.
If moving the adverb produces an odd rhythm, consider rewriting the sentence instead of tolerating a clumsy construction. -
Use split infinitives only when clearly justified.
If you decide to keep one, be certain it serves clarity or emphasis and that other options genuinely work less well.
9. Conclusion
In contemporary English, split infinitives are no longer universally condemned, but they remain a point of sensitivity in academic and scientific writing. Understanding the structure of the English infinitive and the history of the debate allows you to make informed choices rather than rely on guesswork or habit.
As a researcher or student, you do not need to remove every split infinitive that appears in your first draft. Instead, treat them as features to review with care. When a revision improves clarity and formality at little cost, adopt it. When a split infinitive clearly helps to convey your meaning and no graceful alternative exists, retain it consciously rather than by accident.
The ultimate goal is not to obey a rule mechanically, but to write prose that is precise, readable, and appropriate for its audience. A solid grasp of how infinitives work—and how to handle them with confidence—brings you one step closer to that goal in every thesis chapter and journal article you write.
