B1 Gerunds & Infinitives 12 min read Medium

Forgot to do vs. Forgot doing

Mastering forgot to do vs. forgot doing unlocks precision in expressing memory and tasks.

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

It is important to use the word forget correctly. Using the wrong words changes the meaning.

This helps you speak better. You will not make easy mistakes.

We use to for things we must do. We use -ing for things we did before.

If you use the wrong word, people will not understand you.

This lesson helps you use forget. You will learn the difference. You will speak better.

How This Grammar Works

The difference is about time. Did you forget before or after?
Use forget to for a job you did not do. You wanted to do it, but you forgot.
I forgot to lock the door means the door is open. You did not lock it.
She forgot to reply means she did not send an email.
Use forget with -ing for things you did. You did it, but you do not remember.
I forgot meeting him means you met him before. But you do not remember it.
He completely forgot saying that yesterday implies the words were spoken, but he has no recall of having uttered them.
Here is how to understand the difference:
  • Forget + to + verb: The action is in the future (from the perspective of the forgetting), and it is not completed. It is about a failure to act. The consequence is typically an unfulfilled obligation or a missed opportunity.
  • Forget + verb-ing: The action is in the past (from the perspective of the forgetting), and it was completed. It is about a failure to remember a past act. The consequence is typically a gap in one's personal memory or a surprise at a past action you cannot recall.
I forgot to send it means it is not sent. I forgot sending it means it is sent.
Using the right words is important. People need to know the truth.

Formation Pattern

1
You can use this in the past or present. Just change the word forget.
2
1. Forget with to and a word
3
You planned to do something. But you did not do it.
4
How to say it | What it means | Example
5
| :-------- | :------ | :----------------------- | :-------------------- | :------------------------ | :--------------- |
6
I forget to bring my umbrella. I do not have it.
7
Don't forget to send the email. Please send it.
8
You forgot to confirm your appointment, so it was cancelled.
9
Please don't forget to turn off the stove after cooking.
10
The manager had forgotten to mention the new policy during the briefing, causing confusion.
11
2. Forget + Gerund (verb-ing)
12
2. Forget with an -ing word
13
How to say it | What it means | Example
14
| :-------- | :------ | :----------------------- | :-------------------- | :------------------------ | :--------------- |
15
I forgot meeting him. I met him, but I do not remember.
16
I don't forget meeting you. I remember it well.
17
I forgot asking you that question. I am sorry.
18
Looking at old photos, she realized she had forgotten visiting that ancient temple.
19
It's astonishing how some people forget learning basic math facts they once knew well.
20
You can use forget in many ways. Use to for things you did not do. Use -ing for things you do not remember. Pick the right one to be clear.

When To Use It

Use the right words for your story. This helps people understand you. This is good for work and friends. Learn the rules to speak better.
Forget + to + action (You did not do it)
Use this for plans or jobs. You forgot and did not do the task. We use this often for work.
  • Unfulfilled Obligations or Tasks: For actions you were supposed to perform but neglected. This often carries an implicit sense of regret, an apology, or a consequence for the oversight.
  • I'm so sorry; I completely forgot to send you the updated project timeline. (The timeline was not sent).
  • Remember to turn off all the lights before you leave. Don't forget to lock the main door, too. (These actions must be done).
  • Missed Appointments or Events: When you fail to attend, participate in, or carry out a scheduled event or activity.
  • She felt terrible because she forgot to attend her friend's graduation ceremony. (She did not go to the ceremony).
  • He forgot to pick up his prescription, so he had to go back to the pharmacy later. (The prescription was not collected).
  • Instructions or Reminders: When someone fails to follow a given direction or a self-imposed reminder.
  • The chef forgot to add salt to the soup, making it taste bland. (The salt was not added).
  • I forgot to charge my phone last night, and now the battery is dead. (The phone was not charged).
Forget + action + ing (You do not remember it)
Use this for things you did before. You did it. Now you do not remember it. A friend might tell you the story.
  • Lost Recollection of Past Actions/Events: When you have no memory of doing something that you demonstrably did or that others remember you doing. This conveys genuine lack of recall.
  • Did I really say that? I completely forgot saying it, honestly. (The words were spoken, but you don't remember).
  • She looked at the old photographs and realized she had forgotten visiting that remote island during her childhood. (The visit happened, but the memory was absent).
  • Surprise at Your Own Past Behavior: When you are confronted with information about something you said or did, and you genuinely have no conscious memory of that specific act.
  • He told me we met at the conference, but I forgot meeting him. He seems familiar now. (The meeting occurred, but you can't recall it).
  • I can't believe I forgot leaving the car keys on the kitchen counter instead of in my bag. (The keys were left there, but you forgot the act).
Forget to means you did not do the task. Forget doing means you did it but forgot. Think: did I do the action?

Common Mistakes

Many students make mistakes here. They use rules from their home language. Learn these rules to speak better.
  • Confusing forget to do with forget doing: This is the most prevalent and impactful error. Interchanging these forms leads to a radical shift in meaning, often resulting in miscommunication or conveying an unintended message.
  • Incorrect: I forgot calling you back. (Implies you did call, but don't remember it.)
  • Correct: I forgot to call you back. (Implies you didn't call, which was your intention.)
  • Why it's wrong: The learner fails to differentiate between a forgotten action (infinitive) and a forgotten memory of an action (gerund). They might use the gerund when they truly mean to express an unfulfilled obligation. This can lead to someone thinking you're denying an action you performed when you intended to apologize for an omission.
  • Using a bare infinitive or other incorrect verb form: English grammar is strict about the verb form immediately following forget in these constructions. Using just the base verb or a past participle is incorrect.
  • Incorrect: I forgot send the email. or I forgot sent the email.
  • Correct: I forgot to send the email. or I forgot sending the email.
  • Why it's wrong: This often stems from a lack of familiarity with English verb complement patterns, where certain verbs strictly require infinitives or gerunds, not bare verb forms.
  • Over-reliance on forget to do: Because forget to do (for unfulfilled tasks) is arguably more common in daily communication, some learners might default to it even when forget doing is appropriate. This limits their expressive range and can sound unnatural when describing forgotten memories.
  • Awkward/Less precise: I forgot to meet her before, even though she insists we did.
  • More natural/Correct: I forgot meeting her before, even though she insists we did.
  • Why it's wrong: The learner might not fully appreciate the context where recalling a past event is the central point, rather than an uncompleted task. They might perceive the infinitive as the general

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 Forgot to do vs. Forgot doing
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?

Formality Spectrum

Formal
I neglected to transmit the report.

I neglected to transmit the report. (Workplace communication)

Neutral
I forgot to send the report.

I forgot to send the report. (Workplace communication)

Informal
I totally blanked on the report.

I totally blanked on the report. (Workplace communication)

Slang
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

Examples by Level

1

Don't forget to call me.

2

I forgot to do my homework.

3

Please don't forget to close the door.

4

He forgot to buy milk.

1

I'll never forget meeting the president.

2

Did you forget to bring your passport?

3

She forgot to send the email yesterday.

4

I forgot seeing that movie before.

1

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

2

I completely forgot meeting him at the party last year.

3

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

4

He forgot taking his medicine this morning.

1

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

2

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

3

Have you forgotten to sign the contract?

4

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

1

I forgot to include the citations in the first draft.

2

One never forgets being treated with such kindness.

3

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

4

I forgot having promised to help him move house.

1

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

2

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

3

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

4

She forgot being reprimanded as a child for her curiosity.

Easily Confused

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

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

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

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

Common Mistakes

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.

Sentence Patterns

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.

💡

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.

Pronunciation

/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.

Memorize It

Mnemonic

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

Visual Association

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

Challenge

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

Cultural Notes

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'.

Conversation Starters

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?

Journal Prompts

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?

Common Mistakes

Incorrect

Correct


Incorrect

Correct


Incorrect

Correct


Incorrect

Correct

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. Multiple Choice

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

Practice Exercises

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. Multiple Choice

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 Fill in the Blank

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

✓ Correct! ✗ Not quite. Correct answer: forget to take
Which sentence is correct? Multiple Choice

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 Translation

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 Fill in the Blank

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

✓ Correct! ✗ Not quite. Correct answer: forget to take
Which sentence is correct? Multiple Choice

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 Translation

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

FAQ (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

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

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