B2 Verb Moods 11 min read ふつう

逃したチャンス：「Could have」の使い方（実現しなかった可能性）

「could have」を使いこなせば、過去の選択や「実現しなかった可能性」について、もっとはっきり気持ちを伝えられるようになりますよ。これはまさに「過去の可能性」を語るための「魔法のフレーズ」です！
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Grammar Rule in 30 Seconds

Use 'could have' to talk about things that were possible in the past but didn't actually happen.

  • Use 'could have' + Past Participle for missed opportunities. Example: 'I could have won.'
  • Use 'couldn't have' for things that were impossible. Example: 'I couldn't have known.'
  • Never use 'could of'—it is always 'could have' or the contraction 'could've'.
Subject + ☁️ could + ⏳ have + ✅ Verb (V3)

Overview

古いインスタグラムの写真を見ていて、「うわ、このネオンカラーのパンツ、絶対履くべきじゃなかった…」と思ったことはありませんか？さて、今日は「すべきだった（*should* have）」ことの話ではありません。あなたの人生の「マルチバース（もしもの世界）」についてお話しします。そう、could have です。この文法は、過去に可能だったけれど、実際には起こらなかったことについて話すためのツールです。コンサートに行くチャンスがあったけれど、家で Netflix を見ることにしたとか。ミームを見るのに夢中で飛行機に乗り遅れそうになったけれど、ギリギリで間に合ったとか。これは「もし〜だったら？」という文法の世界です。あなたが選ばなかった、もう一つの選択肢の幽霊のようなものです。
英語の世界では、これを「実現しなかった可能性（Unrealized Possibility）」と呼びます。難しい言葉に聞こえますが、要するに「開いていたけれど、通らなかったドア」のことです。思い出話をしたり、Zoom 会議を欠席した理由を説明したり、あるいは悪いことが起こらなくて済んだ安堵感を表現したりするのに最適です。例えば、スマホをトイレに落としそうになったと想像してみてください。「ふぅ！危うく大惨事になる（could have）ところだった！」と言いますよね（しかも、かなり高くつく大惨事です）。私たちは、過去のポテンシャルや逃した機会、あるいは単に「もしあの朝5時のワークアウトを計画通りにこなしていたら…」なんて白昼夢に浸るときにこれを使います。

How This Grammar Works

could have を、通らなかった道だけを見せてくれるタイムマシンのように考えてみてください。英語では、気分や可能性を示すために could のような「助動詞」を使います。そこに have と「過去分詞（done、seen、eaten のような動詞の第3形態）」を加えることで、その可能性を過去へと押し戻します。
今「できる（*can*）」ことについて話しているわけではありません。別の結果もあり得た過去の特定の瞬間を振り返っているのです。3つのセリフの選択肢があるビデオゲームのようなものです。あなたは選択肢Aを選びましたが、後になって、選択肢Bを選んでいればもっとゴールドをゲットできていた（could have）かもしれないと気づくのです。重要なのは、could have は常に「そのことは実際には起こらなかった」ということを暗に示しているという点です。もし私が「2011年にビットコインを買うことができた（I could have bought Bitcoin）」と言ったら、私が今はプライベートアイランドに住む億万長者ではないことが自動的にわかります。私はおそらくただここにいて、あなたのためにこのガイドを書いているだけなのです。
また、could have を短縮して could've と言うことがよくあります。発音は「クドゥヴ（could-uv）」のように聞こえます。ネイティブスピーカーは99%の確率でこう話します。毎回フルで「could have」と言うと、人間に化けようとしているロボットのように聞こえるかもしれません。正直なところ、SF映画をたくさん見ている私たちなら、その結末がどうなるか知っていますよね。カジュアルなチャットでは短縮形を使いましょう！

Formation Pattern

1
この「もしもの世界」マシンを作るには、3つの材料が必要です。サワードウ・ブレッドのレシピに従うよりも簡単です、約束します。
2
主語 (I, you, he, she, it, we, they) から始めます。
3
魔法のフレーズ could have (または短縮形の could've) を加えます。
4
メインの動詞の 過去分詞（Past Participle） で締めくくります。
5
構成: [主語] + [could have] + [過去分詞]
6
肯定: "You could've won the game!" (試合に勝てたのに！実際は勝たなかった)。
7
否定: "I couldn't have known." (知る由もなかった。知ることは不可能だった)。
8
疑問:
Could you have helped me?
(助けてくれることは可能だった？実際は助けてくれなかったけれど)。
9
プロのヒント: he、she、it が主語でも、have が has に変わることはありません。
She could have gone
と言い、
She could has gone
とは言いません。助動詞 could がすべてを固定してくれるのです。have という動詞のボディガードのような存在です。

When To Use It

この文法をポケットから取り出すべき主な場面は3つあります。
  • 後悔や逃した機会: 過去について少し悲しくなったり、内省したりするときに使います。
    I could have studied harder for that exam.
    (そのテストのためにもっと勉強できたのに。実際は、猫がパルクールをしている TikTok を6時間見て過ごしてしまった)。
  • 安堵（ネガティブな可能性）: 悪いことが起こりそうだったけれど、運よく免れたときに使います。
    You could have fallen!
    (落ちる可能性があったよ！ 落ちなくてよかったね。病院の食事はひどいから)。
  • 過去についての推測: 何が起こったか確信はないけれど、可能性を考えているときに使います。
    Where is Sarah? She could have missed her bus.
    (サラはどこ？ バスに乗り遅れたのかもしれない)。
また、丁寧な表現としても優れています。誰かが重い箱を運ぶのに苦労していたら、
I could have helped you with that!
(手伝えたのに！) と言えます。その瞬間は過ぎてしまったけれど、手伝う意思があったことを示せます。ただし、5階まで運び終わった後に言うのはやめましょう。ただ嫌味に聞こえるだけですから。

Common Mistakes

  • Could Of の罠: これはネイティブスピーカーでもやってしまう、一番多い間違いです！ could've が could of のように聞こえるため、多くの人がそう書いてしまいます。絶対に could of と書いてはいけません。文法的に「違法」です。あなたがそれをタイプするたびに、どこかで文法の先生がため息をついています。
  • 間違った動詞の形: 常に 過去分詞（past participle） を使ってください。
    I could have go
    や
    I could have went
    とは言いません。
    I could have gone
    が正解です。動詞の「第3の形」のルールだと覚えておきましょう。
  • 'Have' を忘れる: I could gone と言ってしまう学習者がいます。これでは未来から来た秘密の言語を話しているように聞こえます。可能性を過去に結びつけるには、その have が必要です。
  • 実際に起こったことに使う: もし本当に店に行ったのなら、
    I could have gone to the store
    とは言いません。あくまで「もしもの世界」のシナリオにのみ使います。

Contrast With Similar Patterns

  • Could have vs. Should have: これが最大の違いです。Could have は「可能だった」という意味。Should have は「すべきだった（いい考えだった、あるいは義務だった）」という意味です。
  • Could have:
    I could have eaten the whole cake.
    (ケーキを全部食べる能力はあったけれど、食べなかった)。
  • Should have:
    I should have eaten the whole cake.
    (素晴らしいケーキだったから、食べなかったことを後悔している)。
  • Could have vs. Can: Can は現在。Could have は過去です。
  • I can swim
    (今、泳ぐ能力がある)。
  • I could have swam across that lake
    (あの時、湖を泳いで渡るチャンスはあったけれど、代わりにボートを選んだ)。
  • Could have vs. Must have: Must have は、何かが起こったとほぼ100%確信しているときに使います。
  • She must have forgotten
    (彼女は忘れたに違いない)。
  • She could have forgotten
    (忘れたのかもしれないし、スマホの充電が切れただけかもしれない)。

Quick FAQ

Q

could have と might have は同じですか？

ほとんど同じです！ どちらも過去の可能性を示します。Could have は通常、あなたに能力や機会があったことを示唆し、might have はより「運」や「偶然」の要素が強いです。

Q

未来のことに could have は使えますか？

いいえ。未来の可能性には単に could を使います。

I could go tomorrow.
could have は厳密に過去を振り返るときだけに使います。

Q

なぜみんな coulda と言うのですか？

それは超カジュアルなスラングです。友達とすごく速く話すときに使う言葉です。

I coulda been a star! (スターになれたかもしれないのに！)
でも、Zoom での採用面接などでは使わないでくださいね。

Q

不可能なことに couldn't have を使ってもいいですか？

はい！ "He couldn't have stolen the cookies; he was with me the whole time! (彼がクッキーを盗んだはずがないよ。ずっと私と一緒にいたんだから！)" 友達（あるいは飼い猫）を弁護するのに最適です。

Forming the Past Modal

Subject Modal Auxiliary Past Participle (V3)
I / You / He / She
could
have
done
It / We / They
could
have
seen
I / You / He / She
couldn't
have
known
It / We / They
couldn't
have
been

Contractions

Full Form Contraction Pronunciation Hint
could have
could've
sounds like 'could-uv'
could not have
couldn't have
sounds like 'couldnt-uv'
could not
couldn't
standard past negative

Meanings

Expresses that something was possible in the past, or that someone had the ability to do something, but they did not do it.

1

Unrealized Opportunity

A choice was available but not taken.

“We could have taken the train, but we drove instead.”

“She could have been a doctor if she hadn't quit school.”

2

Past Speculation

Guessing about what was possible in a past situation.

“He could have gotten lost in the city.”

“The keys could have fallen out of your pocket.”

3

Past Impossibility (Negative)

Expressing that something was not possible, even if we tried.

“I couldn't have finished it without your help.”

“He couldn't have been at the party; he was with me.”

Reference Table

Reference table for 逃したチャンス：「Could have」の使い方（実現しなかった可能性）
使い方 意味 例
実現しなかった可能性
可能だったのに、実際には起こらなかったこと。
`I could have gone.`
後悔・批判
過去の行動や不行動に対する悲しみや非難を表す。
`You could have helped.`
使われなかった過去の能力
能力はあったのに、それを使わなかったこと。
`She could have played guitar.`
仮定法過去完了
過去の出来事が違っていたら、結果も違っただろうという仮定。
`If I had known, I could have come.`
否定形
過去に不可能だったこと。
`I couldn't have known.`

フォーマル度スペクトル

フォーマル
The company could have implemented a more robust strategy.

The company could have implemented a more robust strategy. (Work performance)

ニュートラル
We could have done a better job on the project.

We could have done a better job on the project. (Work performance)

カジュアル
We could've done way better.

We could've done way better. (Work performance)

スラング
Man, we coulda crushed that.

Man, we coulda crushed that. (Work performance)

Could Have: 実現しなかった過去の可能性

Could Have

形

  • Subject + could + have + V3 She could have called.
  • 否定形: couldn't have + V3 He couldn't have known.

主な使い方

  • 逃した機会 I could have gone.
  • 後悔・批判 You could have warned me.
  • 使われなかった能力 She could have learned.

よくある間違い

  • could of ❌ instead of could have
  • V1 or V2 ❌ instead of V3 (Past Participle)

仮定法との関係

  • 仮定法過去完了 If I had known, I could have helped.

Could Have vs. Should Have vs. Would Have の比較

Could Have
過去の可能性・能力 I could have bought it (had the chance, didn't).
実現しなかった潜在能力 She could have been a doctor.
Should Have
過去の義務・良い考え I should have studied (it was my duty/a good idea).
後悔・批判 You should have told me.
Would Have
仮定法過去完了の過去の結果 If I had known, I would have come.
過去の意欲（満たされなかった） I would have helped, but I couldn't.

「Could Have」を使うのはいつ？

1

過去について話していますか？

YES
次のステップへ進む。
NO
このルールは当てはまりません。「could」（現在/未来の可能性）を検討してください。
2

何かが可能だった（能力や機会があった）のに、実際には起こりませんでしたか？

YES
`could have + 過去分詞 (V3)` を使います。
NO
次のステップへ進む。
3

過去に起こらなかったが、起こり得た行動について、後悔や軽い批判を表現していますか？

YES
`could have + 過去分詞 (V3)` を使います。
NO
「might have」（より弱い可能性）または「should have」（義務/良い考え）を検討してください。

「Could Have」のよくあるシナリオ

😔

日々の後悔

  • • I could have saved more money.
  • • You could have called me back.
🚪

逃した機会

  • • We could have taken that trip.
  • • She could have gotten the job.
💬

仮定法過去完了の文脈

  • • If I had studied, I could have passed.
  • • If she had left, he could have been angry.
💪

使われなかった能力

  • • He could have been a great musician.
  • • I could have learned to code.
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レベル別の例文

1

I could run fast when I was young.

I was able to run fast.

2

She could not come to the party.

She was not able to come.

3

Could you see the moon?

Were you able to see it?

4

They could speak English.

They had the skill.

1

I could have bought that shirt.

I had the money, but I didn't buy it.

2

We could have won the game.

We were close, but we lost.

3

You could have told me!

Why didn't you tell me?

4

He could have been late.

Maybe he was late.

1

I could have gone to university, but I started working.

I had the opportunity but chose work.

2

It could have been a mistake.

Perhaps it was a mistake.

3

She couldn't have known about the party.

It was impossible for her to know.

4

They could have finished earlier if they tried.

They had the capacity to finish fast.

1

If I'd had more time, I could have done a better job.

With more time, better quality was possible.

2

You could have at least offered to help!

I am annoyed you didn't offer.

3

The accident could have been much worse.

It was possible for more damage to occur.

4

He couldn't have stolen the money; he was in jail.

It is logically impossible.

1

The project could have been salvaged had the management intervened.

Intervention would have made success possible.

2

I could have sworn I left my keys on the table.

I was very sure, but I might be wrong.

3

Such a discovery could not have been made without modern technology.

Modern tech was a necessary condition.

4

We could have been looking at a total economic collapse.

That was a realistic, though avoided, possibility.

1

One could have argued that the treaty was doomed from the outset.

A valid argument existed for its failure.

2

The sheer audacity of the plan could have only been matched by its failure.

Only failure was as great as the audacity.

3

He couldn't have been more helpful if he'd tried.

He was extremely helpful.

4

The implications could have reverberated for decades.

Long-term effects were possible.

間違えやすい

Missed Chances: How to use 'Could have' (Unrealized Possibility) 対 Could have vs. Should have

Learners use 'could' when they mean 'it was a good idea' (should).

Missed Chances: How to use 'Could have' (Unrealized Possibility) 対 Could have vs. Must have

Using 'could' for a logical certainty.

よくある間違い

✗

I could to go.

✓

I could go.

Modal verbs never take 'to'.
✗

I can go yesterday.

✓

I could go yesterday.

Use 'could' for past ability.
✗

I could have go.

✓

I could have gone.

You must use the past participle (V3).
✗

She could has won.

✓

She could have won.

Modal auxiliaries always use 'have', never 'has'.
✗

I could of seen it.

✓

I could have seen it.

Phonetic error: 'of' is never used here.
✗

I could have win.

✓

I could have won.

Forgetting the irregular past participle.
✗

He couldn't have been there, could he?

✓

He couldn't have been there, could he?

Actually correct, but learners often use 'mustn't have' which is rare/incorrect for deduction.

文型パターン

I could have ___, but I ___.

You could have at least ___!

If I had known, I could have ___.

Real World Usage

Job Interview common

I could have stayed at my last job, but I wanted a new challenge.

Texting Friends very common

U could've told me u were leaving!!

Police Report occasional

The suspect could have entered through the back window.

Sports Commentary constant

He could've scored if he'd passed the ball!

Doctor's Office common

This condition could have been prevented with early screening.

Travel/Airlines common

We could have missed our connection due to the delay.

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💡

耳を澄ませて聞いてみよう！

速く話す時、「could have」は「could've」のように聞こえることが多いんです。これが「could of」と間違われる原因になることも。たとえ微妙でも「v」の音を聞き分けられるように、耳を鍛えましょう。「of」は前置詞、「have」は助動詞なので、意味が全く違いますよ！
⚠️

「should have」と混同しないで！

「could have」は「可能性はあったけど、しなかった」というニュアンスです。一方、「should have」は「〜すべきだったのにしなかった」という、もっと強い後悔や義務感を表します。伝えたいニュアンスに合わせて、使い分けが大切ですよ:
I should have studied harder.
🎯

仮定法過去完了で実力アップ！

「could have」は、仮定法過去完了（If + 過去完了, would/could/might + have + V3）で大活躍します。この構文をマスターすれば、過去の仮定の話が格段にスムーズになりますよ:
If I had known, I could have helped you.
🌍

オンラインでのトーンに注意！

「could have」は基本的に中立的な表現ですが、オンラインやメッセージで誰かの過去の行動を批判する意図で使うと、きつく聞こえることがあります。直接的な批判を避けたい場合は、「maybe」や「it seems」のような言葉を加えて、柔らかく伝えましょう:
Maybe you could have tried a different approach.
💡

「道の分岐点」をイメージしよう！

「could have」を使う時は、過去に自分や誰かが選択を迫られた瞬間を想像してみてください。一つの道を選んだけど、「could have」は選ばなかったもう一つの道を指し示しています:
I could have taken the other road.

Smart Tips

Use 'You could have...' followed by a small action. It sounds less aggressive than a direct 'You didn't...'

You didn't call me. → You could have called me.

Mentally correct it to 'could have'. This will help you avoid picking up bad habits from native speakers.

I could of gone. → I could have gone.

Use 'could have' for multiple possibilities. If you only have one theory, use 'must have'.

He must have gone to the store (but maybe the gym). → He could have gone to the store, or he could have gone to the gym.

Always double-check the V3 form. 'Could have saw' is a common error; it must be 'could have seen'.

I could have saw it. → I could have seen it.

発音

/kʊdəv/

The Schwa Reduction

In 'could have', the 'have' is almost never stressed. It reduces to a schwa sound /əv/.

/kʊd/

The 'L' is Silent

The 'l' in 'could' is never pronounced.

Criticism Intonation

You could have TOLD me! (Stress on 'told')

Expresses annoyance.

暗記しよう

記憶術

COULD HAVE: C-hance O-mitted U-nder L-ikely D-esires. (A chance you didn't take).

視覚的連想

Imagine a 'Sliding Doors' scenario where you see two versions of yourself: one who did the action and one who didn't. 'Could have' is the ghost version of you.

Rhyme

If it could have been but was not so, use 'could have' to let us know!

Story

John was late for his flight. He could have taken a taxi, but he took the bus. He could have arrived on time, but the bus broke down. Now he's at the airport, thinking about what could have been.

Word Web

could'veunrealizedpossibilityV3regretspeculationcounterfactual

チャレンジ

Write down three things you 'could have' done this morning but chose not to (e.g., I could have eaten a donut).

文化メモ

Often used for 'polite reproach' to avoid direct confrontation. Saying 'You could have mentioned it' is a very British way of saying 'I am angry you didn't tell me.'

The phrase 'Coulda, woulda, shoulda' is a common idiom used to tell someone to stop complaining about the past because it can't be changed.

In sports commentary, 'could have' is used constantly to analyze 'what if' moments in a game.

From Old English 'cuðe' (past of 'cunnan' - to know/be able).

会話のきっかけ

“

What is something you could have done differently in your last job?

“

If you had been born in a different country, how could your life have been different?

“

Think of a famous movie. How could the ending have been better?

“

What's a skill you could have learned as a child but didn't?

日記のテーマ

Write about a 'near miss' you experienced. What could have happened?
Reflect on a major life decision. What other paths could you have taken?
Critique a historical event. How could the leaders have acted differently?

よくある間違い

Incorrect

正解

Incorrect

正解

Incorrect

正解

Incorrect

正解

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Test Yourself

文を完成させるために正しい形を選びましょう。

If I had known about the sale, I ___ that new laptop.

✓ Correct! ✗ Not quite. Correct answer: could have bought
仮定法過去完了の文では、過去の仮定の結果を表すために「could have + 過去分詞」を使います。「Could of」はよくある間違いです。
文中の間違いを見つけて修正しましょう。 Error Correction

Find and fix the mistake:

She could have went to the gym, but she chose to relax.

✓ Correct! ✗ Not quite. Correct answer: She could have gone to the gym, but she chose to relax.
「could have」の後には、動詞の過去分詞（V3）形が来なければなりません。「go」の過去分詞は「gone」であり、「went」ではありません。
実現しなかった過去の可能性を正しく表している文を選びましょう。 選択問題

正しい文を選んでください:

✓ Correct! ✗ Not quite. Correct answer: He could have won the race, but he tripped near the finish line.
正しい構文は「could have」の後に動詞の過去分詞（V3）が続く形です。「won」は「win」のV3形です。
単語を並べ替えて、文法的に正しい文を作りましょう。 Sentence Reorder

Arrange the words in the correct order:

All words placed

Click words above to build the sentence

✓ Correct! ✗ Not quite. Correct answer: You could have warned me
「could have」の構文は「主語 + could + have + 過去分詞 (V3) + 目的語」です。

Score: /4

練習問題

8 exercises
Complete the sentence with 'could have' and the correct form of the verb in brackets.

I ___ (buy) that house, but it was too expensive.

✓ Correct! ✗ Not quite. Correct answer: could have bought
We use 'could have' + the past participle 'bought'.
Find the mistake in the sentence. Error Correction

Find and fix the mistake:

She could of been a famous singer.

✓ Correct! ✗ Not quite. Correct answer: could of
It should be 'could have' or 'could've'.
Which sentence expresses that something was impossible? 選択問題

Select the correct option.

✓ Correct! ✗ Not quite. Correct answer: I couldn't have gone.
'Couldn't have' expresses past impossibility.
Rewrite the sentence using 'could have'. Sentence Transformation

It was possible for him to win, but he didn't.

✓ Correct! ✗ Not quite. Correct answer: He could have won.
'Could have won' replaces 'It was possible for him to win'.
Fill in the missing part of the dialogue. Dialogue Completion

A: Why didn't you call me? B: I'm sorry, I ___ (lose) my phone.

✓ Correct! ✗ Not quite. Correct answer: could have lost
B is speculating about a past possibility.
Which of these is a 'missed opportunity'? Grammar Sorting

Pick the correct sentence.

✓ Correct! ✗ Not quite. Correct answer: I could have studied more for the test.
This shows an action that was possible but not done.
Is this rule true or false? True False Rule

You can use 'could has' if the subject is 'he' or 'she'.

✓ Correct! ✗ Not quite. Correct answer: False
It is always 'could have', regardless of the subject.
Put the words in the correct order. Sentence Building

have / they / told / could / us

✓ Correct! ✗ Not quite. Correct answer: They could have told us.
The order is Subject + could + have + V3.

Score: /8

Practice Bank

11 exercises
「could have」の正しい形で文を完成させましょう。 穴埋め問題

The concert tickets were expensive, but I ___ them if I had saved more.

✓ Correct! ✗ Not quite. Correct answer: could have afforded
文法的な間違いを見つけて修正しましょう。 Error Correction

If she had taken the earlier flight, she could of arrived on time.

✓ Correct! ✗ Not quite. Correct answer: If she had taken the earlier flight, she could have arrived on time.
実現しなかった過去の能力を正しく表している文を選びましょう。 選択問題

どちらの文が正しいですか？

✓ Correct! ✗ Not quite. Correct answer: He could have spoken French fluently if he hadn't stopped practicing.
次の文を英語に翻訳しましょう: 翻訳

次の文を英語に翻訳しましょう: 'Podríamos haber evitado el problema si hubiéramos sido más cuidadosos.'

✓ Correct! ✗ Not quite. Correct answer: ["We could have avoided the problem if we had been more careful.","We could've avoided the problem if we'd been more careful."]
単語を並べ替えて、意味の通る文を作りましょう。 Sentence Reorder

これらの単語を並べ替えて文を作りましょう:

✓ Correct! ✗ Not quite. Correct answer: I couldn't have known about the change
文の始まりと正しい終わりを組み合わせましょう。 Match Pairs

文を正しく完成させるために、節を組み合わせましょう:

✓ Correct! ✗ Not quite. Correct answer: matched
会話を完成させるのに最適な選択肢を選びましょう。 穴埋め問題

A: Why didn't you join us last night? B: I ___ to the party, but I was exhausted.

✓ Correct! ✗ Not quite. Correct answer: could have come
「could have」に関連する間違いを修正しましょう。 Error Correction

If you had warned him, he could have avoid the accident.

✓ Correct! ✗ Not quite. Correct answer: If you had warned him, he could have avoided the accident.
文の英語訳を提供しましょう。 翻訳

次の文を英語に翻訳しましょう: 'Ella podría haber aceptado la oferta de trabajo.'

✓ Correct! ✗ Not quite. Correct answer: ["She could have accepted the job offer.","She could've accepted the job offer."]
単語を並べ替えて正しい文を作りましょう。 Sentence Reorder

これらの単語を並べ替えましょう:

✓ Correct! ✗ Not quite. Correct answer: We could have gone earlier if we had
「could have」と一緒に正しい動詞の形を使っている文はどれですか？ 選択問題

正しい文を選びましょう:

✓ Correct! ✗ Not quite. Correct answer: He could have eaten the whole cake.

Score: /11

よくある質問 (8)

They are often interchangeable for speculation. However, `could have` suggests a stronger ability or possibility, while `might have` suggests a weaker chance.

Generally, no. In formal essays or business reports, use the full `could have`.

Because the contraction `could've` sounds exactly like 'could of'. It's a common spelling mistake based on sound.

No, `could have` is strictly for the past. For the future, use `could` or `might`.

It's an idiom meaning 'I was as happy as possible.' It uses the negative to show that more happiness was impossible.

Not always. It can also mean relief (`We could have died!`) or simple speculation (`He could have forgotten`).

Put 'could' before the subject: `Could he have known?`

Yes! It's often the result clause: `If I had seen him, I could have spoken to him.`

Scaffolded Practice

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1

2

2

3

3

4

4

Mastery Progress

Needs Practice

Improving

Strong

Mastered

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In Other Languages

Spanish high

Podría haber + participio

Spanish speakers sometimes use the imperfect 'podía' where English requires 'could have'.

French high

Aurait pu + infinitif

French uses the infinitive after 'pu', while English uses the past participle.

German moderate

Hätte ... können

The word order is very different, with verbs often moving to the end.

Japanese low

...できたかもしれない

Japanese doesn't have a single 'modal perfect' structure like English.

Arabic moderate

كان بإمكانه أن...

Arabic uses a noun-based structure for ability.

Chinese low

本来可以...

Chinese relies on adverbs rather than verb conjugation to show the past.

Learning Path

Prerequisites

Previous
過去の強い不信 (Can't Have + V3)
Next
Ought To: 助言と義務

Learn These First

B1 Builds On

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