Grammar Rule in 30 Seconds
To ask questions, swap 'Can' and the subject; to say no, just add 'not' to 'can'.
- Questions: Move 'Can' to the front. Example: 'Can you swim?'
- Negatives: Use 'cannot' or 'can't'. Example: 'I can't drive.'
- No 'To': Never use 'to' after can. Example: 'I can't go' (NOT 'I can't to go').
Overview
can について詳しく解説します。この can は「助動詞（じょどうし）」と呼ばれるグループの仲間です。文字通り「動詞を助ける」役割を持っており、動詞の前に置くだけで「〜ができる」という能力や、「〜してもいい」という許可の意味を付け加えることができます。can という言葉を一つ覚えるだけで、表現の幅がぐんと広がります。しかも、英語の動詞の多くは主語（I, He, Sheなど）によって形が変わることがありますが、can はどんな主語が来ても形が変わらないという、初心者にとって非常に優しいルールを持っています。can のような「助動詞」が英語の中でどのように機能するのか、日本語と比較しながら見てみましょう。ここには、日本語を母国語とする私たちが特に意識すべき3つの大きなポイントがあります。- 肯定文（ふつうの文）:
I can speak English.(主語 + can + 動詞) - 疑問文（質問の文）:
Can you speak English?(Can + 主語 + 動詞)
He や She の時に s をつける「三単現のs」というルールがありますが、can にはそのルールが適用されません。これは日本語の感覚に近いため、覚えやすいはずです。I can...(私は〜できる)He can...(彼は〜できる) ←He cansとは言いません！They can...(彼らは〜できる)
can の後ろに来る動詞は、必ず辞書に載っているそのままの形（原型）を使います。日本語で「食べることが〜」と言うときに「食べる」という辞書形を使うのと似ていますが、英語では to を入れたり -ing をつけたりしたくなる誘惑に勝たなければなりません。work) | 助動詞 (can) |He works. (sが必要) | He can work. (変化なし) |Do you work? (Doが必要) | Can you work? (canを前に出す) |I don't work. (don'tが必要) | I cannot work. (notをつけるだけ) |speak, go) |can の後ろに not を置きます。これには主に2つの書き方があります。cannot: 1語で書くのが正式な形です。少し硬い響きがあり、強調したい時やビジネス文書で使われます。can't:cannotを短くした形（短縮形）です。日常会話やSNS、友人とのLINEなどでは、ほとんどの場合このcan'tが使われます。
I can't swim.(私は泳げません。)He can't come to the party.(彼はパーティーに来られません。)We cannot accept this.(私たちはこれを受け入れることはできません。)
can の位置を入れ替えます。文の最後にはクエスチョンマーク ? を忘れずにつけ、語尾を上げて発音します。Can you help me?(手伝ってくれますか？)Can she play the piano?(彼女はピアノが弾けますか？)
Yes, I can.(はい、できます。)No, I can't.(いいえ、できません。)
What, Where, When などの疑問詞を置きます。What can I do for you?(何かお手伝いしましょうか？ / 直訳：私はあなたのために何ができますか？)Where can we buy tickets?(どこでチケットを買えますか？)How can I get to Shibuya station?(渋谷駅にはどうやって行けますか？)
can は非常に用途が広い言葉です。日常生活のどのようなシーンで使うのか、具体的に見ていきましょう。I can speak a little English.(英語が少し話せます。)My brother can cook very well.(兄は料理がとても上手です。)Can you drive?(運転はできますか？)
Can I use your pen?(ペンを借りてもいい？)You can park your car here.(ここに車を停めてもいいですよ。)Can I open the window?(窓を開けてもいいですか？)
Can you repeat that, please?(もう一度言っていただけますか？)Can you tell me the way to the hotel?(ホテルへの道を教えてくれますか？)
It can be very cold in Hokkaido.(北海道はとても寒くなることがあります。)Even experts can make mistakes.(専門家でも間違いを犯すことはあります。)
Do を使ってしまうミスplay, speak など）は Do you...? で疑問文を作りますが、can は自分自身で疑問文を作れる「強い言葉」です。そのため、Do の助けは必要ありません。- 間違い:
Do you can swim?(×) - 正しい:
Can you swim?(○) - なぜ間違う？: 日本語では「泳ぐ（動詞）」も「泳げる（可能）」も同じように質問するため、英語でも全ての質問に
Doを使いたくなってしまうからです。
to を入れてしまうミスto play のように to をつける習慣があるため、can の後ろにも to を入れたくなることがあります。- 間違い:
I can to play tennis.(×) - 正しい:
I can play tennis.(○) - なぜ間違う？: 日本語の「テニスをすること（不定詞的表現）ができる」という構造を直訳しようとしてしまうためです。
canの後は「裸の動詞（原型）」と覚えましょう。
- 間違い:
Can speak English.(×) - 正しい:
I can speak English.(○) - なぜ間違う？: 日本語では「英語、話せます」だけで完璧な文章になるため、つい
Iを忘れがちです。英語では「誰が」できるのかを必ず明示しましょう。
can と似た意味を持つ表現や、使い分けが必要な表現と比較してみましょう。これにより、can の立ち位置がより明確になります。can | 最も一般的でカジュアル。能力・許可・依頼。 | Can you help me? |could | can よりも丁寧で控えめな響き。 | Could you help me? (手伝っていただけますか？) |may | 非常にフォーマルな許可。先生や上司に対して使う。 | May I come in? (失礼してもよろしいでしょうか？) |be able to | can よりも「一時的に〜できた」という事実や、少し硬い響き。 | I was able to finish the task. (課題を終えることができた。) |can を使いこなせるようになることを目標にしましょう。丁寧にお願いしたい時（レストランで注文する時など）は、Can I have...? に please を添えるだけで十分に礼儀正しくなります。can't と cannot はどちらを使うべきですか？can't が使われます。発音もしやすく自然です。テストや正式な手紙、あるいは「絶対にダメ！」と強調したい時には cannot を使います。なお、can not と2語に分けるのは一般的ではありません。必ず cannot と1語で書きましょう。Can I...? は失礼になりませんか？May I...? や Could I...? を使うと「おっ、この人は礼儀正しいな」という印象を与えます。can't の発音が聞き取れません。コツはありますか？can は弱く「クン」のように発音されることが多いのに対し、否定の can't は「キャント」と強く、はっきり発音されます。最後の t は飲み込むように発音されることが多いですが、その分、前の「キャ」の部分が強調されます。相手が強く「キャ」と言ったら否定だと判断してほぼ間違いありません。can の疑問文と否定文は、英語の基礎中の基礎ですが、これをマスターするだけであなたの世界は大きく広がります。コンビニで Can I have a plastic bag?（袋をいただけますか？）と言ってみたり、同僚に Can you check this?（これ確認してくれる？）と頼んでみたり、日常の小さな場面からぜひ使ってみてください。応援しています！The Unchanging 'Can'
| Subject | Negative (Short) | Negative (Long) | Question |
|---|---|---|---|
|
I
|
can't
|
cannot
|
Can I...?
|
|
You
|
can't
|
cannot
|
Can you...?
|
|
He/She/It
|
can't
|
cannot
|
Can he/she/it...?
|
|
We
|
can't
|
cannot
|
Can we...?
|
|
They
|
can't
|
cannot
|
Can they...?
|
Contractions of Can
| Full Form | Contraction | Usage |
|---|---|---|
|
cannot
|
can't
|
Standard speaking
|
|
can not
|
n/a
|
Rare emphasis
|
Meanings
Used to ask about or deny someone's ability, permission, or the possibility of an action occurring.
Ability
Asking if someone has the skill or physical power to do something, or stating they lack it.
“Can you speak Spanish?”
“I can't play the piano.”
Permission
Asking for or denying the right to do something in a specific situation.
“Can I go to the bathroom?”
“You can't park your car here.”
Possibility
Questioning if something is possible or stating that it is impossible.
“Can it be true?”
“It can't be 10:00 PM already!”
Reference Table
| 文の種類 | 主語 | Can/Can't | 主な動詞（原形） | 例文 |
|---|---|---|---|---|
|
肯定文
|
I
|
can
|
swim
|
I can swim.
|
|
疑問文
|
Can
|
you
|
help?
|
Can you help?
|
|
疑問文
|
Can
|
he
|
speak English?
|
Can he speak English?
|
|
否定文
|
She
|
can't
|
come
|
She can't come.
|
|
否定文
|
We
|
cannot
|
see
|
We cannot see.
|
|
疑問文
|
Can
|
they
|
play?
|
Can they play?
|
フォーマル度スペクトル
May I please have a glass of water? (Restaurant/Home)
Can I have a glass of water, please? (Restaurant/Home)
Can I get some water? (Restaurant/Home)
Can I grab a water? (Restaurant/Home)
Can: 疑問文と否定文
疑問文
- Can + Subject + Verb? Can you swim?
- 許可 Can I sit here?
- 依頼 Can you help me?
否定文
- Subject + can't + Verb I can't dance.
- Subject + cannot + Verb We cannot wait.
- 不能 He can't see.
- 許可の否定 You can't go.
主要ルール
- 三人称単数に's'なし He can, not He cans.
- 常に動詞の原形 Can you speak, not to speak.
- 'do/does'なし Can you, not Do you can.
疑問文の作り方: 'Can' vs. 他の動詞
'Can'を使った質問または否定文の作り方
能力や許可を表現したいですか？
質問ですか？
否定文ですか？
主な動詞に'to'や'-s'がついていますか？
'Can'と'Can't'を使う時
能力
- • Can you swim?
- • I can't dance.
- • She can speak French.
許可
- • Can I sit here?
- • You can't go yet.
- • We can leave now.
依頼
- • Can you help me?
- • Can I have water?
- • Can you close the door?
可能性
- • It can be cold.
- • This can't be true.
- • He can be late.
レベル別の例文
Can you swim?
Can you swim?
I can't cook.
I cannot cook.
Can he play football?
Can he play football?
They cannot come today.
They cannot come today.
Can I open the window?
Can I open the window?
You can't smoke here.
You are not allowed to smoke here.
Can you tell me the time?
Can you tell me the time?
We can't find the museum.
We are unable to find the museum.
Can't you see I'm busy?
Can't you see I'm busy?
It can't be a mistake.
It is impossible that it is a mistake.
Can anything be done about it?
Is there any possible solution?
I can't help but wonder why.
I cannot stop myself from wondering why.
Cannot we find a better solution?
Is it not possible for us to find a better solution?
You can't have finished already!
I don't believe you have finished already.
Can such a thing really happen?
Is it actually possible for such a thing to occur?
One cannot simply walk into Mordor.
It is not possible for a person to just walk in.
Can you not make that noise?
Please stop making that noise.
The importance of this cannot be overstated.
This is extremely important.
Can it be that she forgot?
Is it possible that she forgot?
I can't say I'm surprised.
I am not surprised at all.
Try as he might, he cannot but fail.
No matter how hard he tries, he will inevitably fail.
Can we but hope for the best?
Is there anything else we can do except hope?
The results can't have been more disappointing.
The results were as disappointing as possible.
One can't very well ask for a refund now.
It is socially awkward or impossible to ask for a refund now.
間違えやすい
Learners use 'can' for permission and 'may' for ability incorrectly.
Learners try to use 'can' in the future or past perfect.
Using 'can' for past abilities.
よくある間違い
Do you can swim?
Can you swim?
I can to play.
I can play.
He cans swim.
He can swim.
I no can go.
I can't go.
Can you to help me?
Can you help me?
I don't can come.
I can't come.
Can you speaking English?
Can you speak English?
I will can go tomorrow.
I will be able to go tomorrow.
It's important to can swim.
It's important to be able to swim.
I haven't could sleep.
I haven't been able to sleep.
文型パターン
Can you ___?
I can't ___ because ___.
Can I ___ please?
Why can't we ___?
Real World Usage
Can u come tonight?
Can I see your boarding pass?
Can you work on weekends?
Can I have the burger without onions?
I can't even!!
Can you feel this?
いつも動詞の原形！
「Do/Does」は使わないで！
短縮形がベスト！
「Can」で丁寧に！
発音を聞き取ろう！
Smart Tips
Remember the 'Inversion Rule': just swap the first two words of the statement. No extra words allowed!
Always use 'cannot' as one single word. Writing 'can not' is a common typo even for natives.
Listen for the vowel length and the stress. 'Can't' is usually longer and louder than the weak 'can'.
Switch from 'Can I' to 'Could I'. It's a small change that makes a big difference in tone.
発音
The Weak 'Can'
In positive sentences and questions, 'can' is usually unstressed and sounds like /kən/ (rhymes with 'sun').
The Strong 'Can't'
The negative 'can't' is always stressed. In American English, it's /kænt/. In British English, it's often /kɑːnt/.
Rising Intonation
Can you help me? ↗
Standard yes/no question tone.
暗記しよう
記憶術
CAN is a CAPTAIN: He doesn't need a 'Do-Assistant' to lead the sentence.
視覚的連想
Imagine a giant 'X' over the word 'DO' whenever you see 'CAN'. Also, imagine 'CAN' and the 'SUBJECT' on a playground see-saw, swapping places for questions.
Rhyme
To ask a question, don't be slow: move 'Can' to the front and you're good to go!
Story
A robot named 'Can' is very independent. He refuses to hold hands with 'To' and he hates the letter 'S'. He also likes to jump to the front of the line whenever someone asks him a question.
Word Web
チャレンジ
Look around your room. Find 3 things you CAN do (e.g., 'I can see a lamp') and 3 things you CAN'T do (e.g., 'I can't fly'). Then, ask a friend or Siri/Google 'Can you...?' questions for 2 minutes.
文化メモ
The pronunciation of 'can't' is a major dialect marker. Americans use a flat 'a' (like 'cat'), while many British speakers use a broad 'a' (like 'car').
While 'Can I...?' is standard, adding 'please' is culturally expected in service industries to avoid sounding demanding.
In older generations or very traditional schools, using 'can' for permission is still sometimes corrected, though this is fading.
From the Old English 'cunnan', which meant 'to know' or 'to know how to'.
会話のきっかけ
Can you play any musical instruments?
Can you speak more than two languages?
Can you cook a traditional dish from your country?
Can you imagine living in a different country?
日記のテーマ
よくある間違い
Test Yourself
___ you speak French?
Find and fix the mistake:
He can't to play the piano.
Translate into English: 'No puedo ir a la fiesta.'
Answer starts with: ["I...
正しい文を選んでください:
Score: /4
練習問題
8 exercises___ you speak English?
I ___ (can) swim. I am afraid of water.
Find and fix the mistake:
She can't to drive a car.
help / you / me / can / ?
He ___ come.
1. Can you swim? | 2. Can he drive? | 3. Can they sing?
A: Can I sit here? B: No, sorry, you ___.
We add 's' to 'can' when the subject is 'he' or 'she'.
Score: /8
Practice Bank
13 exercisesWe ___ see the screen clearly.
Do you can speak English?
正しい文を選んでください:
Translate into English: 'Ella no puede venir mañana.'
これらの単語を並べ替えて文にしてください:
主語と正しい形を合わせてください:
Sorry, I ___ help you right now.
She cans sing very well.
能力を正しく尋ねる文はどれですか？
Translate into English: 'Puedes ayudarme con mi tarea?'
これらの単語を並べ替えて文にしてください:
___ I borrow your pen?
正しい文はどれですか？
Score: /13
よくある質問 (8)
Yes, but it's very rare. It is usually only used for extreme emphasis, like 'I can NOT believe you did that!'. Normally, use `cannot` or `can't`.
Because `can` is a modal verb. Modal verbs are like 'super verbs'—they don't need the help of `do` to make questions or negatives.
You can use it for future arrangements (e.g., 'I can meet you tomorrow'), but for general future ability, you must use `will be able to`.
`can't` is for speaking and casual writing. `cannot` is for formal documents and academic essays. They mean the same thing.
Yes, `Can I have...` is very common and polite if you add `please`. If you want to be extra formal, you can use `Could I have...`.
It's a regional accent difference. Americans say it with a short 'a' (cat), and many British people say it with a long 'a' (car). Both are correct!
No. Modal verbs like `can` are always followed by the 'bare infinitive', which means the verb without the word `to`.
Mostly, yes. `Can` is more common in daily speech. `Be able to` is used when `can` is grammatically impossible (like after 'will' or 'have').
Scaffolded Practice
1
2
3
4
Mastery Progress
Needs Practice
Improving
Strong
Mastered
In Other Languages
Poder
English 'can' has no conjugation; Spanish 'poder' does.
Pouvoir
French uses 'est-ce que' or inversion; English uses only inversion for 'can'.
Können
German conjugates 'können' (ich kann, du kannst).
Potential form (~eru/~aru) or 'dekiru'
Japanese uses verb suffixes; English uses a separate modal verb.
Yastati'u (يستطيع)
Arabic 'can' is a complex conjugated verb; English 'can' is a simple particle.
Huì (会) / Néng (能)
Chinese has two words for 'can' based on the type of ability.
Learning Path
Prerequisites
Learn These First
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