Grammar Rule in 30 Seconds
A split infinitive occurs when you place an adverb between the particle 'to' and the base verb for emphasis or clarity.
- Standard: 'to' + 'verb' (to go). Split: 'to' + 'adverb' + 'verb' (to boldly go).
- Use it to avoid ambiguity: 'to quickly leave' is clearer than 'quickly to leave'.
- Modern style allows it, but some formal academic circles still prefer avoiding it.
Overview
to + verb があります。ここには埋めるべき素晴らしい隙間があるのです。To boldly go where no man has gone before を聞いたことがあるでしょう。このフレーズは、古い考えの文法教師たちへの究極の反論です。不定詞の分割は、to と verb の間に副詞（adverb）を置いたときに起こります。何十年もの間、人々はこれを間違いだと考えてきました。彼らは To go boldly と言うことを求めました。しかし To go boldly はビクトリア朝の詩のように聞こえます。To boldly go はミッション（使命）のように聞こえます。C2レベルでは、単にルールを学ぶだけではありません。スタイルを持ってルールを破る方法を学ぶのです。これを使って文章に彩りを添えましょう。より自然でリズム感のある響きになります。不定詞を一度も分割しないと、ロボットのように聞こえるかもしれません。あるいは、ひどく退屈な教科書のようです。私たちはそれを望んでいません。あなたの英語に魂を込めたいのです。How This Grammar Works
to finish のような標準的な不定詞を用意します。どのように終わらせるのかを強調したいとします。finally のような副詞を選び、それを真ん中に落とし込みます。これで to finally finish となります。これは単に反抗的であるということではありません。強調したい部分をまさに適切な場所に置くということです。通常、副詞は直後に来る動詞を修飾します。不定詞の中に置くことで、強い結びつきが生まれます。意味はパンチが効いて明確になります。サンドイッチのように考えてください。to と verb がパンで、副詞が美味しい具材です。具材がなければ、ただのトーストです。C2試験でただのトーストを出したい人はいません。
Formation Pattern
to に動詞の原形が続く形です。例：to understand。
fully。
to と verb の間に副詞を挿入します。
to + adverb + verb です。例：to fully understand。
When To Use It
I want to personally thank you for the opportunity. これは I want to thank you personallyよりもずっと誠実に聞こえます。緊張感を高めるためにクリエイティブな文章で使いましょう。言い換えがぎこちなかったり、曖昧だったりするときに使いましょう。副詞を別の場所に置くと、意味が完全に変わってしまうことがあります。
She decided to quickly leaveと言えば明確です。
She decided quickly to leaveと言うと、決断が早かったのか、去るのが早かったのか分かりません。不定詞を分割することで、その謎が解けます。トレンドに乗っているように見せるために、SNSのキャプションで使いましょう。
Trying to actually live my best life. これは Trying to live my best life actuallyよりも響きます。
Common Mistakes
to と verb の間にフレーズ丸ごとを置かないでください。To as quickly as humanly possible run は災難です。1語か2語にとどめましょう。もう一つのミスは、不要な副詞を「押し込む」ことです。動詞がすでに副詞の意味を含んでいるなら、分割しないでください。To loudly shout は冗長です。叫ぶ（shout）はすでに声が大きい（loudly）からです。非常に特定の意図がある場合を除き、not のような否定語で分割するのは避けましょう。To not go が標準です。To never again see は効果的なドラマチックな分割です。しかし to not ever go はただ散らかっているだけです。目立とうとして分割しないでください。リズムが崩れるなら、それはミスです。あなたのゴールは、滑らかで洗練された雰囲気であり、文法の衝突事故ではありません。Contrast With Similar Patterns
- 分割なし：
He prepared to enter silently.
（入ることに焦点）。 - 分割あり：
He prepared
（静かであることに焦点）。to silently enter.
He silently prepared to enter.これでは準備が静かだったのであって、必ずしも入る動作が静かだったとは限りません。配置がすべてです。C2英語では、これらの小さな変化があなたの武器になります。単にデータを送信するのではなく、言葉で絵を描くのです。見せたい場所にカメラを向けるために分割を使いましょう。
Quick FAQ
To slowly and carefully walk はOKですが、それ以上は混乱を招きます。To boldly go です。宇宙、それは文法にとっても最後のフロンティアです。Infinitive Placement Comparison
| Type | Structure | Example | Effect |
|---|---|---|---|
|
Standard
|
to + verb + adverb
|
To go boldly
|
Neutral/Traditional
|
|
Split
|
to + adverb + verb
|
To boldly go
|
Emphatic/Rhythmic
|
|
Negative Standard
|
not + to + verb
|
Not to fail
|
Formal/Standard
|
|
Negative Split
|
to + not + verb
|
To not fail
|
Conversational/Strong
|
|
Compound Split
|
to + adv + and + adv + verb
|
To fully and clearly see
|
Highly Descriptive
|
Meanings
The practice of placing a word or phrase (usually an adverb) between 'to' and the bare infinitive form of a verb.
Emphasis
Using the split to draw specific attention to the manner of the action.
“I want you to really think about this.”
“She needs to actually try for once.”
Clarity/Ambiguity Avoidance
Splitting the infinitive to ensure the adverb modifies the correct verb in a complex sentence.
“He agreed to immediately help us (He will help now).”
“He agreed immediately to help us (The agreement happened now).”
Negative Splitting
Placing 'not' between 'to' and the verb for stylistic weight.
“The challenge is to not fail.”
“I was told to not worry.”
Reference Table
| 構造 | 例文 | 効果・ニュアンス | 使用シーン |
|---|---|---|---|
|
分離不定詞 (Split)
|
`to boldly go`
|
副詞が動詞を直接修飾し、強調される
|
明快さ、強調、自然なリズム
|
|
非分離 (副詞が前)
|
`boldly to go`
|
非常に不自然で、現代英語では稀
|
ほぼ使われません
|
|
非分離 (副詞が後)
|
`to go boldly`
|
強調が弱まり、時に意味が曖昧になる
|
副詞を強調したくない時
|
|
複数副詞の挿入
|
`to very quickly understand`
|
複数の修飾語で精度を高める
|
詳細な説明が必要な時
|
|
副詞句の挿入
|
`to with great skill perform`
|
描写が豊かになるが、重たくなりやすい
|
特定の効果を狙う時のみ
|
|
否定副詞
|
`to never yield`
|
強い否定と明確な決意を表す
|
絶対的な拒絶や不在を伝える時
|
フォーマル度スペクトル
To understand the situation fully (General comprehension)
To fully understand the situation (General comprehension)
To really get what's going on (General comprehension)
To lowkey get the vibe (General comprehension)
分離不定詞の世界
メリット
- 強調 Focus on adverb
- 明快さ Avoid ambiguity
- 流れ Natural sound
例文
- to boldly go Star Trek classic
- to quickly run Speed of action
- to always remember Continuous action
副詞の種類
- -ly 副詞 quickly, fully
- 短い副詞 just, never
- 副詞句 with precision
避けるべき時
- 分離しすぎ Too many words
- 不自然な響き Sounds bad
- 超保守的な場 Traditional readers
分離 vs 非分離：ニュアンスとインパクト
この不定詞、分離させるべき？
明快さや強調が高まりますか？
音読した時に自然ですか？
挟む言葉が多すぎませんか？
相手は超保守的な文法家ですか？
よく使われる分離副詞
強調
- • truly
- • really
- • completely
- • fully
- • totally
様態
- • quickly
- • gently
- • carefully
- • boldly
- • efficiently
頻度・タイミング
- • always
- • never
- • often
- • soon
- • just
程度
- • further
- • greatly
- • radically
- • barely
レベル別の例文
I want to really help you.
I want to really help you.
Try to slowly speak.
Try to slowly speak.
He needs to quickly run.
He needs to quickly run.
I like to always win.
I like to always win.
You need to carefully open the box.
You need to carefully open the box.
She decided to never go back.
She decided to never go back.
We hope to soon see you.
We hope to soon see you.
It is hard to perfectly cook rice.
It is hard to perfectly cook rice.
The manager asked us to seriously consider the offer.
The manager asked us to seriously consider the offer.
I was told to not touch the buttons.
I was told to not touch the buttons.
They want to significantly improve the software.
They want to significantly improve the software.
He tried to quietly enter the room.
He tried to quietly enter the room.
The government plans to further investigate the matter.
The government plans to further investigate the matter.
It is essential to properly maintain your vehicle.
It is essential to properly maintain your vehicle.
She was able to successfully complete the marathon.
She was able to successfully complete the marathon.
We need to effectively communicate our goals.
We need to effectively communicate our goals.
The witness was asked to truthfully and accurately recount the events.
The witness was asked to truthfully and accurately recount the events.
The author tends to deliberately obscure the protagonist's motives.
The author tends to deliberately obscure the protagonist's motives.
The company sought to aggressively expand its market share.
The company sought to aggressively expand its market share.
It is a mistake to simply assume that the data is correct.
It is a mistake to simply assume that the data is correct.
The diplomat's task was to subtly yet firmly convey the administration's displeasure.
The diplomat's task was to subtly yet firmly convey the administration's displeasure.
To truly understand the poem, one must look beyond the literal meaning.
To truly understand the poem, one must look beyond the literal meaning.
The board decided to irrevocably and unconditionally terminate the contract.
The board decided to irrevocably and unconditionally terminate the contract.
He was determined to not only survive but to actually thrive in the new environment.
He was determined to not only survive but to actually thrive in the new environment.
間違えやすい
Learners often place adverbs in positions where they could modify the preceding or following verb.
よくある間違い
I want to really to go.
I want to really go.
To go really.
To really go.
He decided to not to eat.
He decided to not eat.
I hope to quickly and without any trouble finish.
I hope to finish quickly and without any trouble.
He failed to completely and utterly and without reservation apologize.
He failed to apologize completely, utterly, and without reservation.
文型パターン
It is important to ___ ___.
The goal is to ___ and ___ ___.
Real World Usage
I hope to significantly contribute to your team.
I need to literally go right now.
The study aims to better understand the underlying causes.
The parties agree to mutually terminate the agreement.
I'm about to finally post the vlog!
Be sure to thoroughly whisk the eggs.
明快さと流れを最優先に
to boldly use itとしましょう！
詰め込みすぎに注意
to quickly and efficiently finish程度に留めるのがスマートです。
自分の「耳」を信じて
English often values natural rhythm over rigid rules.
相手を見極める
In most modern communication, you are absolutely fine.
Smart Tips
Try splitting the infinitive to see if it adds more 'punch' to your sentence.
Switch to 'to not' for a more modern, conversational feel.
Split the infinitive to ensure the adverb only modifies the action verb.
Do NOT split. Move the long phrase to the end of the sentence.
発音
Stress the Adverb
When splitting an infinitive, the stress usually falls on the adverb to highlight the manner of the action.
Rising-Falling
to BOLDly go
Conveys confidence and emphasis.
暗記しよう
記憶術
Remember 'Star Trek': To BOLDLY go. If Captain Kirk can do it, you can too!
視覚的連想
Imagine a giant wedge (the adverb) being driven between the words 'to' and 'verb'. The wedge makes the whole structure stronger and more visible.
Rhyme
When 'to' and 'verb' are split apart, the adverb speaks from the heart.
Story
A grammarian in 1860 tried to glue 'to' and 'run' together with Latin glue. But the English language was too strong; it popped an 'adverb' right in the middle to show everyone how it's done.
Word Web
チャレンジ
Write three sentences about your career goals using split infinitives (e.g., 'I want to significantly increase...').
文化メモ
Americans are generally very comfortable with split infinitives, especially in media and business.
Some older British style guides (and older generations) may still view it as a sign of 'lazy' writing, though this is changing rapidly.
The phrase 'To boldly go' from Star Trek is the most famous split infinitive in history and is often used to defend the construction.
The 'rule' against split infinitives was popularized by Henry Alford in 1864, who based it on Latin grammar.
会話のきっかけ
What is one thing you want to completely change about your routine?
In your opinion, is it better to slowly build a career or to quickly reach the top?
日記のテーマ
よくある間違い
Test Yourself
The manager asked her ___ complete the urgent task.
We aim to make sure entirely that the data is accurate.
to entirely make sure とすることで、確認の「徹底ぶり」が明確に伝わります。Choose the correct sentence:
Score: /3
練習問題
8 exercisesThe company needs...
If you want to win, you need ___.
Find and fix the mistake:
He decided quickly to leave the party.
I decided ___.
Splitting an infinitive is a grammatical error in modern English.
Identify the split infinitive:
A: Should I tell him the truth? B: I think you need ___.
It is easy ___.
Score: /8
Practice Bank
12 exercisesIt's important ___ remember your roots.
The company decided ___ restructure its global operations.
I need to ensure thoroughly that all safety protocols are followed.
She resolved to, after much deliberation, resign from her position.
Choose the correct sentence:
Choose the correct sentence:
Translate into English: '目標は品質を劇的に向上させることです。'
Translate into English: '彼女は試験のために真剣に勉強し始めました。'
Arrange these words into a sentence:
Arrange these words into a sentence:
Match the infinitive phrase beginnings with their appropriate split adverbs.
Match the split infinitive on the left with an equivalent or closest unsplit version on the right.
Score: /12
よくある質問 (8)
Only if it makes the sentence confusing or ugly. If you put a 10-word phrase between 'to' and the verb, it's 'wrong' stylistically, but not grammatically.
Many teachers still follow 19th-century rules based on Latin. In Latin, you can't split an infinitive because it's one word. English is different!
Yes, but 'to not' is often more emphatic. 'I chose not to go' is neutral. 'I chose to not go' sounds like a stronger decision.
Yes. Most modern academic journals and style guides (like MLA or Chicago) allow it for the sake of clarity.
It's an adverb that sits between two verbs, making it unclear which one it modifies. Splitting the infinitive solves this by 'locking' the adverb to the second verb.
Yes, e.g., 'to fully and completely understand'. Just don't overdo it, or the sentence will become hard to follow.
You can say 'to clearly be' or 'to be clearly'. Both are common, but 'to clearly be' is the split form.
The Star Trek intro: 'To boldly go where no man has gone before.'
Scaffolded Practice
1
2
3
4
Mastery Progress
Needs Practice
Improving
Strong
Mastered
In Other Languages
Infinitive + Adverb
English infinitives are two words; Spanish are one.
Infinitive + Adverb
French cannot split the verb unit.
Adverb + zu + Infinitive
German puts the adverb before the 'to' equivalent.
Adverb + Verb-form
No particle-verb structure to split.
Masdar (Verbal Noun)
Arabic uses noun-based or clause-based structures.
Adverb + Verb
No 'to' particle exists to be split from the verb.
Learning Path
Prerequisites
関連動画
Related Grammar Rules
分詞構文: 動作と主語の一致
Overview インスタグラムのフォロワーに、朝のコーヒーが長い睡眠の後に「リフレッシュした気分（`feeling refreshed`）」だった...
受動態の動名詞と不定詞 (being done / to be done)
Overview 誰かに `being directed`（演出されている）映画の背景キャラクターのような気分になったことはありませんか？あるいは...
Stop + 動名詞 vs. 不定詞: やめる vs. 一時停止する
### Overview 英語の学習を進めていく中で、B1レベル（中級）に到達すると、単に単語を並べるだけでなく「ニュアンスの使い分け...
Infinitives and Gerunds: Verb Patterns (Want to Go / Enjoy Going)
## Infinitives and Gerunds: Verb Patterns ### Verbs + to + infinitive - **want**: I want **to eat**. - **need**: She ne...
英語の分詞構文: 同時に2つのことをする (V-ing)
### Overview 英語学習において、CEFR C1レベル、つまり上級レベルに到達しようとする際、避けては通れないのが「情報の凝縮」...
