B1 Gerunds & Infinitives 12 min read ふつう

〜するのを忘れた vs. 〜したのを忘れた

Mastering forgot to do vs. forgot doing unlocks precision in expressing memory and tasks.
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Grammar Rule in 30 Seconds

Use 'to' for tasks you missed and '-ing' for memories you lost.

  • Forgot to do: You didn't do the task. Example: 'I forgot to call him.'
  • Forgot doing: You did it, but don't remember. Example: 'I forgot calling him.'
  • Negative focus: 'Never forget doing' is common for vivid memories.
🧠 + Forget + 📝 (to do) vs. 🧠 + Forget + 🎞️ (doing)

Overview

### Overview
英語の学習を進めていく中で、多くの日本人が「壁」に突き当たるのが、動詞の後に続く形によって意味がガラリと変わるパターンです。特に forget（忘れる）という動詞は、その典型例と言えます。forget to do と forget doing。この2つの違いを正確に理解し、使い分けることは、単なる文法の知識を超えて、あなたの英語の「解像度」を一段階引き上げるために不可欠です。
私たち日本人が英語を話す際、どうしても日本語の「〜するのを忘れた」という一律の表現に引きずられてしまいがちです。しかし、英語においては、その「忘れた内容」が「これからすべきこと（未来・義務）」なのか、それとも「すでに経験したこと（過去・記憶）」なのかによって、文法構造を明確に使い分ける必要があります。この区別ができないと、例えばビジネスの場で「メールを送るのを忘れた（送っていない）」と言いたいのに、「メールを送った記憶がない（実際には送ったかもしれない）」という意味で伝わってしまい、大きな誤解を招く可能性すらあります。
本稿では、B1レベル（中級）の学習者が、自信を持ってこれらの表現を使い分けられるよう、その背後にある言語的なロジックから、具体的な活用シーン、そして日本人が陥りやすい落とし穴までを徹底的に解説します。単に暗記するのではなく、「なぜそうなるのか」という感覚を掴んでいきましょう。
### How This Grammar Works
forget + to do と forget + doing の最大の違いは、「忘れる」という行為と「動詞の内容」の間の時間的な関係性にあります。英語の不定詞（to do）と動名詞（doing）が持つ根本的なイメージを理解すると、この違いがスッと腑に落ちるはずです。
まず、forget + to + verb（不定詞）について考えてみましょう。英語の to は「矢印（→）」のイメージを持っており、常に「これから向かう先」、つまり「未来」や「未完了」のことを指します。したがって、forget to do は「（これから）〜することを忘れる」という意味になります。つまり、「すべきことがあったのに、それを忘れて実行しなかった」という状況を指します。ここでは、動作そのものは「未完了」です。
一方で、forget + verb-ing（動名詞）はどうでしょうか。動名詞（-ing）は、生き生きとした「動作そのもの」や「すでに起こっていること」、あるいは「過去の経験」を指す性質があります。そのため、forget doing は「（過去に）〜したことを忘れる」という意味になります。つまり、「実際に行為は完了しているが、その時の記憶が抜け落ちている」という状況を指します。ここでは、動作は「完了」しています。
この違いを、日本語の感覚と比較してみましょう。
| 英語の構造 | 時間の焦点 | 日本語のニュアンス | 動作の状態 |
|---|---|---|---|
| forget to do | 未来・予定 | 〜し忘れる | していない（未完了） |
| forget doing | 過去・経験 | 〜したことを忘れる | した（完了） |
日本語では「〜するのを忘れた」という一つの言い方で両方をカバーできてしまうことが多いため、日本人はこの使い分けに苦労します。しかし、英語では「行為の有無」に関わる重大な差なのです。この「未来（未完了）の to」と「過去（完了）の ing」というコア・イメージを常に意識してください。
### Formation Pattern
形自体は非常にシンプルです。forget の時制を変化させ、その後に不定詞か動名詞を置くだけです。ただし、文脈によって forget 自体が現在形、過去形、現在完了形など様々に変化することに注意しましょう。
#### 1. forget to do のパターン（〜し忘れる）
  • 肯定文: Subject + forget(s) / forgot + to + Base Verb
  • I forgot to lock the door.（ドアに鍵をかけ忘れた。）
  • 否定文: Subject + didn't forget + to + Base Verb
  • I didn't forget to buy the milk.（牛乳を買うのを忘れなかった。＝ちゃんと買った。）
  • 命令文: Don't forget to + Base Verb
  • Don't forget to submit the report.（レポートを提出するのを忘れないで。）
#### 2. forget doing のパターン（〜したことを忘れる）
  • 肯定文: Subject + forget(s) / forgot + Verb-ing
  • I forgot meeting him before.（以前彼に会ったことを忘れていた。）
  • 否定文: Subject + won't forget + Verb-ing
  • I will never forget seeing that beautiful sunrise.（あの美しい日の出を見たことは決して忘れないでしょう。）
注意点: forget doing は、肯定文の過去形（I forgot doing...）で使われると「やった記憶がない」という少し特殊な響きになります。日常会話では「決して忘れない」という強い感情を込めて I will never forget doing... という形で使われることが非常に多いのも特徴です。
### When To Use It
具体的なシチュエーションで、どのように使い分けられるかを見てみましょう。日本の日常生活やビジネスシーンを想定するとイメージが湧きやすくなります。
#### forget to do を使う場面：タスクや義務の失念
これは「うっかり〜し忘れた」という、日常生活で最も頻繁に起こるミスを表現する時に使います。ToDoリストにある項目をチェックし忘れたような状態です。
  • 職場での連絡ミス:
I forgot to reply to the client's email.
（クライアントのメールに返信するのを忘れました。）
※返信はまだ「していない」状態です。
  • 家事や日課:
I forgot to turn off the air conditioner when I left home.
（家を出る時、エアコンを消し忘れました。）
※エアコンは「ついたまま」です。
  • リマインド（念押し）:
Please don't forget to bring your business card to the meeting.
（会議に名刺を持ってくるのを忘れないでくださいね。）
#### forget doing を使う場面：記憶や経験の欠落・保持
これは、行為自体は行ったものの、そのエピソードが記憶から消えている、あるいはその素晴らしい経験を記憶に留めておきたい時に使います。
  • 記憶の曖昧さ（デジャヴのような状況）:
I forgot telling you that story. Did I really tell you?
（その話を君にしたこと、忘れてたよ。本当に話したっけ？）
※話したという「事実」はあるが、「記憶」がない状態です。
  • 強い思い出（決して忘れない）:
I will never forget visiting Kyoto for the first time.
（初めて京都を訪れた時のことは、決して忘れません。）
※訪問したという「経験」を大切にしている表現です。
  • 無意識の行動:
He forgot locking the door, so he went back to check it.
（彼は鍵をかけたことを忘れてしまったので、確認しに戻った。）
※実際には鍵を「かけた」が、その記憶が不安になった状態です。
### Common Mistakes
日本人の英語学習者が特にはまりやすい罠がいくつかあります。これらは日本語の構造と英語の構造のズレから生じるものです。
#### 1. 「〜したのを忘れた」をすべて to do で言ってしまう
日本語では「宿題をするのを忘れた（未完了）」も「以前会ったのを忘れた（経験）」も、どちらも「〜するのを／したのを」という似た形で表現できてしまいます。そのため、経験について話しているのに、ついつい to do を使ってしまうミスが多発します。
  • 間違い: I forgot to meet her at the party last year.
  • 正解: I forgot meeting her at the party last year.
to meet と言うと、「去年のパーティーで彼女に会う予定だったのに、会い忘れた（会わなかった）」という意味になってしまいます。「会ったことはあるけれど、その事実を忘れていた」と言いたい場合は、必ず -ing を使いましょう。
#### 2. Don't forget doing という不自然な形
「〜したことを忘れないで」と言いたい時に、Don't forget doing と言ってしまうことがありますが、これは文脈によっては非常に不自然です。通常、誰かに「〜するのを忘れないでね」と注意を促す場合は、これから行う動作を指すので、100% Don't forget to do になります。
  • 不自然: Don't forget buying the souvenir!
  • 自然: Don't forget to buy the souvenir!
「お土産を買うのを忘れないでね！」というリマインドなら、必ず to buy です。-ing を使うのは、「お土産を買ったというあの素晴らしい体験を忘れないで」という非常に特殊な（そして日常ではあまり使わない）文脈に限られます。
#### 3. 状態動詞との組み合わせミス
know や believe などの「状態」を表す動詞は、通常 -ing 形で forget の後に来ることは稀です。例えば「それを知っていたことを忘れた」と言いたい場合は、I forgot that I knew it. のように that 節を使うのが一般的です。何でもかんでも -ing にすれば良いわけではない点に注意しましょう。
### Contrast With Similar Patterns
forget と同じように、後ろに to do が来るか doing が来るかで意味が変わる動詞は他にもあります。これらをセットで覚えると、英語の「未来（to）vs 過去（ing）」の感覚がより研ぎ澄まされます。
| 動詞 | + to do (未来・義務・未完了) | + doing (過去・経験・完了) |
|---|---|---|
| forget | 〜し忘れる（やっていない） | 〜したことを忘れる（やった） |
| remember | 忘れずに〜する（これからやる） | 〜したことを覚えている（やった） |
| regret | 残念ながら〜する（これから言う） | 〜したことを後悔する（やった） |
| stop | 〜するために立ち止まる（目的） | 〜するのをやめる（中断） |
| try | 〜しようと努力する（未達成） | 試しに〜してみる（実行済み） |
例えば remember の場合：
  • Please remember to call me.（忘れずに電話してね。＝電話はこれから）
  • I remember calling you.（君に電話したのを覚えているよ。＝電話はした）
このように、forget で学んだルールは他の主要な動詞にも応用可能です。この共通のパターンに気づくことが、中級レベルから上級レベルへステップアップする鍵となります。
### Quick FAQ
Q1: forget の後に that 節（forget that...）を使うのと、どう違いますか？
A1: forget that... は非常に万能です。forget doing とほぼ同じ意味（〜したという事実を忘れる）で使われることが多いですが、より説明的で丁寧な響きになります。例えば、I forgot meeting him. よりも I forgot that I had met him. の方が、いつ会ったのかなどの詳細情報を付け加えやすいため、日常会話でも頻繁に使われます。迷ったら that 節を使うのも一つの手ですが、感情を込めたい時や簡潔に言いたい時は doing が好まれます。
Q2: I forgot to do it. と I forgot doing it.、どちらが日常会話でよく使われますか？
A2: 圧倒的に I forgot to do it.（〜し忘れた）の方が出現頻度が高いです。私たちは日々、鍵をかけ忘れたり、メールを出し忘れたり、宿題を忘れそうになったりするからです。forget doing（〜したことを忘れる）を使う場面は、「自分の記憶力の欠如」を話題にする時や、感動的な思い出について語る時に限られるため、まずは to do の方を完璧にマスターすることをお勧めします。
Q3: 「〜するのを忘れないように」を so that などで言い換えられますか？
A3: はい、可能です。例えば Don't forget to lock the door. は、Make sure you lock the door.（必ず鍵をかけるようにしてね）や Remember to lock the door.（忘れずに鍵をかけてね）と言い換えることができます。forget は「失敗」に焦点を当てた言葉なので、よりポジティブに「〜することを確実にしてね」と言いたい時は Make sure to... や Remember to... を使うと、相手に与える印象が柔らかくなります。
---
先生からのメッセージ
forget to do と forget doing の違い、いかがでしたか？日本語では曖昧にされがちな「行為の有無」が、英語では不定詞と動名詞という形の差によって明確に区別されていることがお分かりいただけたと思います。
最初は「どっちだっけ？」と迷うかもしれませんが、そんな時は 「これからすること（to）」か「すでにしたこと（ing）」か という時間軸を思い浮かべてください。この感覚が身につくと、英語を話す時にいちいち頭の中で日本語に訳さなくても、状況に応じて自然と形が選べるようになります。日々の生活の中で、「あ、これし忘れた！」と思った時に I forgot to... と独り言を言ってみることから始めてみましょう。頑張ってくださいね！

Conjugating 'Forget' with Complements

Tense Forget Form Infinitive (Task) Gerund (Memory)
Present Simple
forget / forgets
I forget to call.
I forget calling.
Past Simple
forgot
I forgot to call.
I forgot calling.
Present Perfect
have forgotten
I've forgotten to call.
I've forgotten calling.
Future
will forget
I'll forget to call.
I'll forget calling.
Negative Future
will never forget
I'll never forget to call.
I'll never forget calling.

Common Contractions

Full Form Contraction Example
I did not forget
I didn't forget
I didn't forget to pay.
I will not forget
I won't forget
I won't forget to write.
I have forgotten
I've forgotten
I've forgotten to ask.

Meanings

The verb 'forget' changes meaning depending on whether it is followed by an infinitive (to + verb) or a gerund (verb + -ing).

1

Failure to perform a task

Using the infinitive indicates that a person did not perform an action because they did not remember it at the necessary time.

“Don't forget to buy milk on your way home.”

“She forgot to tell me about the meeting.”

2

Loss of memory of a past event

Using the gerund indicates that an action was performed in the past, but the person has no mental record or recollection of it.

“I'll never forget meeting you for the first time.”

“He forgot lending me the money, so he asked for it again.”

3

Neglecting a duty (Formal)

In formal contexts, 'forget to' can imply a failure of responsibility rather than just a memory slip.

“The defendant forgot to mention his previous convictions.”

“The company forgot to update its privacy policy.”

Reference Table

Reference table for 〜するのを忘れた vs. 〜したのを忘れた
Form Structure Meaning Example
Affirmative (Task)
Subject + forgot + to + verb
Failed to do something
I forgot to buy bread.
Affirmative (Memory)
Subject + forgot + verb-ing
Did it, but don't remember
I forgot buying bread.
Negative (Task)
Subject + didn't forget + to + verb
Remembered to do a task
I didn't forget to call you.
Negative (Memory)
Subject + will never forget + verb-ing
Will always remember
I'll never forget meeting her.
Question (Task)
Did + subject + forget + to + verb?
Asking if a task was missed
Did you forget to lock up?
Question (Memory)
Have + subject + forgotten + verb-ing?
Asking if a memory is lost
Have you forgotten meeting me?

フォーマル度スペクトル

フォーマル
I neglected to transmit the report.

I neglected to transmit the report. (Workplace communication)

ニュートラル
I forgot to send the report.

I forgot to send the report. (Workplace communication)

カジュアル
I totally blanked on the report.

I totally blanked on the report. (Workplace communication)

スラング
I straight up forgot the report, my bad.

I straight up forgot the report, my bad. (Workplace communication)

The Forget Split

Forget

To + Verb

  • Task Something to do
  • Incomplete Action didn't happen

Verb + ing

  • Memory Something done
  • Complete Action happened

Task vs. Memory

Forget to do
Forgot to pay Debt still exists
Forget doing
Forgot paying Debt is gone

Which one should I use?

1

Did the action happen?

YES
Use -ing (Memory)
NO
Use 'to' (Task)

Common Verbs with 'To'

📅

Daily Tasks

  • • to call
  • • to buy
  • • to lock
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レベル別の例文

1

Don't forget to call me.

No te olvides de llamarme.

2

I forgot to do my homework.

Olvidé hacer mi tarea.

3

Please don't forget to close the door.

Por favor, no olvides cerrar la puerta.

4

He forgot to buy milk.

Él olvidó comprar leche.

1

I'll never forget meeting the president.

Nunca olvidaré conocer al presidente.

2

Did you forget to bring your passport?

¿Olvidaste traer tu pasaporte?

3

She forgot to send the email yesterday.

Ella olvidó enviar el correo ayer.

4

I forgot seeing that movie before.

Olvidé haber visto esa película antes.

1

I forgot to lock the car, so I had to go back.

Olvidé cerrar el coche, así que tuve que volver.

2

I completely forgot meeting him at the party last year.

Olvidé por completo haberlo conocido en la fiesta el año pasado.

3

Don't forget to check the weather before you leave.

No olvides revisar el clima antes de irte.

4

He forgot taking his medicine this morning.

Él olvidó que se tomó su medicina esta mañana.

1

I forgot to mention that the office will be closed on Friday.

Olvidé mencionar que la oficina estará cerrada el viernes.

2

I'll never forget walking across the stage at graduation.

Nunca olvidaré caminar por el escenario en la graduación.

3

Have you forgotten to sign the contract?

¿Has olvidado firmar el contrato?

4

She forgot telling me the secret, so she told me again.

Ella olvidó que me había contado el secreto, así que me lo contó de nuevo.

1

I forgot to include the citations in the first draft.

Olvidé incluir las citas en el primer borrador.

2

One never forgets being treated with such kindness.

Uno nunca olvida ser tratado con tanta amabilidad.

3

He had forgotten to set the alarm, which resulted in a chaotic morning.

Había olvidado poner la alarma, lo que resultó en una mañana caótica.

4

I forgot having promised to help him move house.

Olvidé haber prometido ayudarlo a mudarse.

1

The witness forgot to disclose his financial interest in the company.

El testigo olvidó revelar su interés financiero en la empresa.

2

I shall never forget standing atop the Himalayas, breathless and humbled.

Nunca olvidaré estar de pie en la cima del Himalaya, sin aliento y humilde.

3

To forget to act is one thing; to forget having acted is quite another.

Olvidar actuar es una cosa; olvidar haber actuado es otra muy distinta.

4

She forgot being reprimanded as a child for her curiosity.

Ella olvidó haber sido reprendida de niña por su curiosidad.

間違えやすい

Forgot to do vs. Forgot doing 対 Remember to vs Remember doing

Learners mix up the task/memory distinction just like with 'forget'.

Forgot to do vs. Forgot doing 対 Stop to vs Stop doing

This rule is different. 'Stop to' means you stop one action to start another. 'Stop doing' means you end an action.

Forgot to do vs. Forgot doing 対 Regret to vs Regret doing

Regret to is for giving bad news; Regret doing is for feeling sorry about the past.

よくある間違い

✗

I forgot call him.

✓

I forgot to call him.

You must use 'to' before the verb.
✗

Don't forget buy milk.

✓

Don't forget to buy milk.

Imperatives with forget need 'to'.
✗

I forgot my keys at home.

✓

I left my keys at home.

Use 'leave' for locations, 'forget' for the action of not bringing.
✗

I forgot to meeting him.

✓

I forgot meeting him.

Don't mix 'to' and '-ing'.
✗

I forgot to meeting her last year.

✓

I forgot meeting her last year.

For past memories, use the gerund.
✗

I'll never forget to see the ocean.

✓

I'll never forget seeing the ocean.

If you saw it, use '-ing'.
✗

Did you forget to locking the door?

✓

Did you forget to lock the door?

Questions about tasks use 'to + base'.
✗

I forgot sending the email, so I sent it again.

✓

I forgot to send the email, so I sent it now.

If you sent it again, you didn't forget 'sending' it (the memory), you forgot 'to send' it (the task).
✗

She forgot to having been there.

✓

She forgot having been there.

The perfect gerund doesn't need 'to'.
✗

I forgot to tell you that I already told you.

✓

I forgot telling you that.

Use the gerund to avoid redundancy when discussing the act of speaking.
✗

He forgot to be told.

✓

He forgot being told.

If he was told but doesn't remember, use the passive gerund.
✗

I forgot to mention to have seen him.

✓

I forgot to mention seeing him.

Nested gerunds/infinitives need careful handling.
✗

I forgot to do it yesterday (when I actually did it).

✓

I forgot doing it yesterday.

Misrepresenting the state of the task.

文型パターン

I forgot to ___ because ___.

I'll never forget ___ing ___.

Did you forget to ___ or did you just forget ___ing it?

Having forgotten to ___, I had to ___.

Real World Usage

Texting a friend very common

Sorry, I forgot to reply!

Job Interview occasional

I'll never forget leading my first team project.

Customer Support common

Did you forget to include your order number?

Social Media Caption very common

Never forget chasing sunsets in Bali.

Doctor's Appointment occasional

I forgot taking the pill this morning, so I took another one.

Travel / Airport common

Don't forget to check your gate number.

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💡

The To-Do List Trick

If you can put the action on a 'To-Do' list, use 'to'. If you can put it in a photo album, use '-ing'.
⚠️

The 'Never' Rule

90% of the time you use 'forget + -ing', you will use the word 'never'. If you aren't using 'never', double-check if you really mean a memory.
🎯

Forget vs. Leave

Don't say 'I forgot my phone at home.' Say 'I left my phone at home' or 'I forgot to bring my phone.'
💬

Polite Apologies

In English, 'I forgot to...' is a very standard, polite way to apologize for a small mistake without making a big deal out of it.

Smart Tips

Always use 'to'. You are apologizing for a task you didn't do.

I forgot sending the file. → I forgot to send the file.

Use 'never forget' + '-ing'. It sounds much more natural than 'I will always remember'.

I will always remember our wedding. → I'll never forget getting married to you.

Use the gerund in a question to ask about the memory itself.

Did you forget to lock the door? (Asking if they missed the task) → Do you forget locking the door? (Asking if they have no memory of doing it)

Use 'neglected to' instead of 'forgot to' to sound more professional and precise.

I forgot to include the attachment. → I neglected to include the attachment.

発音

/fərˈɡɒt tə/

Reduction of 'to'

In 'forget to', the 'to' is often reduced to a schwa /tə/.

/fərˈɡɒtɪŋ/

Linking 'forget' and '-ing'

When using the gerund, the final 't' of 'forget' or 'forgot' often links to the vowel of the next word.

Emphasis on 'never'

I will NEVER forget meeting her.

Conveys strong emotional significance.

暗記しよう

記憶術

To is for 'To-Do'; Ing is for 'In the past'.

視覚的連想

Imagine a 'To-Do' list with an empty checkbox for 'Forget to'. Imagine a photo album for 'Forget doing'.

Rhyme

If there's a task you didn't do, use the word that starts with TO. If it's a memory from the spring, use the word that ends in ING.

Story

John had a busy day. He forgot TO buy a ring (so he had no gift). Later, he forgot BUYING the ring (he found it in his pocket and was surprised).

Word Web

TaskMemoryInfinitiveGerundRecallNeglectOmission

チャレンジ

Write down three things you forgot to do yesterday, and one amazing thing you will never forget doing in your life.

文化メモ

British speakers often use 'forgotten' as the past participle, but in casual speech, 'forgot' is sometimes heard. 'I've forgot to do it' is common in some dialects but considered non-standard.

American English strictly uses 'forgotten' as the past participle. 'I've forgotten to...' is the standard way to express a recent missed task.

In corporate settings, saying 'I forgot to...' is seen as taking responsibility. Saying 'I forgot doing...' can sound like you are disorganized or have a poor memory for your own actions.

The word 'forget' comes from Old English 'forgytan', meaning 'to lose grip on' or 'to let go'.

会話のきっかけ

“

What is one thing you always forget to do in the morning?

“

Tell me about a trip you will never forget taking.

“

Have you ever forgotten to bring something important to an exam or interview?

“

Do you ever forget doing something, like locking the door, and have to check twice?

日記のテーマ

Write about a time you forgot to do something important. What were the consequences?
Describe a childhood memory that you will never forget. Use vivid sensory details.
Compare the feeling of forgetting to do a task versus forgetting that you already did it.
Discuss the impact of technology on our memory. Do we forget to do things more often now?

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

Fill in the blank with the correct form of the verb in parentheses.

I forgot ___ (buy) a gift for the party, so I had to stop at the store.

✓ Correct! ✗ Not quite. Correct answer: to buy
The person missed the task of buying a gift, so the infinitive 'to buy' is required.
Choose the sentence that means the action actually happened. 選択問題

Which sentence implies the person has a memory of the event?

✓ Correct! ✗ Not quite. Correct answer: I forgot meeting him.
The gerund 'meeting' indicates a past experience that the person no longer remembers.
Correct the error in the following sentence. Error Correction

Find and fix the mistake:

I'll never forget to see the Eiffel Tower for the first time.

✓ Correct! ✗ Not quite. Correct answer: I'll never forget seeing
Vivid life memories use the gerund form.
Rewrite the sentence using 'forget'. Sentence Transformation

I didn't remember to lock the door.

✓ Correct! ✗ Not quite. Correct answer: I forgot to lock the door.
Not remembering to do a task is the same as forgetting to do it.
Is the following statement true or false? True False Rule

'I forgot to pay the bill' means the bill is still unpaid.

✓ Correct! ✗ Not quite. Correct answer: True
'Forget to' means the action was not completed.
Complete the dialogue. Dialogue Completion

A: Why are you late? B: Sorry, I forgot ___ (set) my alarm.

✓ Correct! ✗ Not quite. Correct answer: to set
Setting the alarm was a task that was missed.
Which form matches 'A memory of the past'? Grammar Sorting

✓ Correct! ✗ Not quite. Correct answer: Forget + doing
The gerund is used for recollections.
Match the sentence to its meaning. Match Pairs

Match each item on the left with its pair on the right:

✓ Correct! ✗ Not quite. Correct answer: 1-No call made, 2-Call made but forgotten
This highlights the core distinction between the two forms.

Score: /8

練習問題

8 exercises
Fill in the blank with the correct form of the verb in parentheses.

I forgot ___ (buy) a gift for the party, so I had to stop at the store.

✓ Correct! ✗ Not quite. Correct answer: to buy
The person missed the task of buying a gift, so the infinitive 'to buy' is required.
Choose the sentence that means the action actually happened. 選択問題

Which sentence implies the person has a memory of the event?

✓ Correct! ✗ Not quite. Correct answer: I forgot meeting him.
The gerund 'meeting' indicates a past experience that the person no longer remembers.
Correct the error in the following sentence. Error Correction

Find and fix the mistake:

I'll never forget to see the Eiffel Tower for the first time.

✓ Correct! ✗ Not quite. Correct answer: I'll never forget seeing
Vivid life memories use the gerund form.
Rewrite the sentence using 'forget'. Sentence Transformation

I didn't remember to lock the door.

✓ Correct! ✗ Not quite. Correct answer: I forgot to lock the door.
Not remembering to do a task is the same as forgetting to do it.
Is the following statement true or false? True False Rule

'I forgot to pay the bill' means the bill is still unpaid.

✓ Correct! ✗ Not quite. Correct answer: True
'Forget to' means the action was not completed.
Complete the dialogue. Dialogue Completion

A: Why are you late? B: Sorry, I forgot ___ (set) my alarm.

✓ Correct! ✗ Not quite. Correct answer: to set
Setting the alarm was a task that was missed.
Which form matches 'A memory of the past'? Grammar Sorting

✓ Correct! ✗ Not quite. Correct answer: Forget + doing
The gerund is used for recollections.
Match the sentence to its meaning. Match Pairs

1. I forgot to call. 2. I forgot calling.

✓ Correct! ✗ Not quite. Correct answer: 1-No call made, 2-Call made but forgotten
This highlights the core distinction between the two forms.

Score: /8

Practice Bank

12 exercises
Choose the correct form 穴埋め問題

Don't ___ your umbrella, it's going to rain later.

✓ Correct! ✗ Not quite. Correct answer: forget to take
Which sentence is correct? 選択問題

Choose the correct sentence:

✓ Correct! ✗ Not quite. Correct answer: He forgot to turn off the lights, and now the room is dark.
Find and fix the mistake Error Correction

I must have forgotten to download that game because I just found it in my downloads folder.

✓ Correct! ✗ Not quite. Correct answer: I must have forgotten downloading that game because I just found it in my downloads folder.
Type the correct English sentence 翻訳

Translate into English: 'Olvidé enviar el correo electrónico.'

✓ Correct! ✗ Not quite. Correct answer: ["I forgot to send the email.","I forgot to send the e-mail."]
Put the words in order Sentence Reorder

Arrange these words into a sentence:

✓ Correct! ✗ Not quite. Correct answer: He forgot telling me about the party.
Match each phrase to its meaning Match Pairs

Match the phrases with the correct meaning:

✓ Correct! ✗ Not quite. Correct answer: matched
Choose the correct form 穴埋め問題

I always ___ my phone at home, it's so frustrating!

✓ Correct! ✗ Not quite. Correct answer: forget to take
Which sentence is correct? 選択問題

Choose the correct sentence:

✓ Correct! ✗ Not quite. Correct answer: She completely forgot seeing that movie, so she watched it again.
Find and fix the mistake Error Correction

I'm so sorry, I totally forgot taking out the trash today.

✓ Correct! ✗ Not quite. Correct answer: I'm so sorry, I totally forgot to take out the trash today.
Type the correct English sentence 翻訳

Translate into English: '¿Olvidaste apagar las luces?'

✓ Correct! ✗ Not quite. Correct answer: ["Did you forget to turn off the lights?"]
Put the words in order Sentence Reorder

Arrange these words into a sentence:

✓ Correct! ✗ Not quite. Correct answer: He forgot admitting his mistake.
Find and fix the mistake Error Correction

I can't believe I forgot to visit London last summer, even though I have photos!

✓ Correct! ✗ Not quite. Correct answer: I can't believe I forgot visiting London last summer, even though I have photos!

Score: /12

よくある質問 (8)

Yes, 'forget about' is usually followed by a noun or a gerund. 'I forgot about the meeting' or 'I forgot about calling him.' It often means you stopped thinking about it.

It is less common than 'forgot to'. Most people use it with 'never' for big memories. In other cases, they might say 'I don't remember doing that' instead.

'Forgot' is for a specific time in the past. 'Have forgotten' is used when the forgetting still affects the present (e.g., 'I've forgotten my password').

This is very rare and usually grammatically incorrect. Stick to 'I forgot doing' for past actions.

Yes! 'Remember to do' is for tasks, and 'Remember doing' is for memories. They are perfect mirrors of each other.

For tasks: 'I didn't forget to...'. For memories: 'I'll never forget...ing'.

'Forgot' is the past tense. 'Forgotten' is the past participle used with 'have' or in the passive voice.

This is common in casual speech, but technically you should use 'left' when you mention a place. 'I left my keys at home' is better.

Scaffolded Practice

1

1

2

2

3

3

4

4

Mastery Progress

Needs Practice

Improving

Strong

Mastered

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In Other Languages

Spanish moderate

Olvidar + infinitivo / Olvidar que...

Spanish lacks a direct gerund equivalent for memories.

French high

Oublier de + infinitif / Oublier d'avoir + participe passé

French uses the infinitive for both, just in different tenses.

German moderate

Vergessen zu + Infinitiv / Vergessen, dass...

German does not use the gerund (-ing) form at all.

Japanese high

〜するのを忘れる / 〜したのを忘れる

Japanese changes the tense of the internal verb (present vs past).

Arabic moderate

Nasiya an + subjunctive / Nasiya annahu + past

Arabic uses clause structures rather than simple verb endings.

Chinese low

忘记 (Wàngjì) + Verb

Chinese relies on aspect markers rather than infinitive/gerund distinctions.

Learning Path

Prerequisites

Previous
Remember + 動名詞 vs 不定詞
Next
Stop + 動名詞 vs. 不定詞: やめる vs. 一時停止する

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