know

know — verb

1. to have facts, information, or answers stored in your mind.

1.verbtransitive / intransitiveA1
Definition

to have facts, information, or answers stored in your mind.

Example

Devika knows the answer to every question in science class.

know + noun phrase

Do you know about the meeting that was added for Friday afternoon?

know + about + noun phrase

Common collocations
  • know the answer
  • know the truth
  • know about
  • know for a fact
  • know full well
Synonyms
Antonyms
  • not know

    the direct opposite; no single-word antonym exists

  • be ignorant of

    formal; suggests a lack of knowledge that one should have

Grammar Patterns

know + noun phrase

know + that-clause

know + wh-clause

know + about

Usage Note

This is the most basic sense of 'know'; use it for any factual information that you can recall or state.

Common Mistakes

I'm knowing the answer.
I know the answer.
'know' is a stative verb and is not used in continuous (-ing) forms.

2. the word used in questions when you are asking somebody to tell you something sp

2.verbtransitiveA2
Definition

the word used in questions when you are asking somebody to tell you something specific that you do not yet know.

Example

Excuse me, do you know where the nearest pharmacy is?

Do you know + wh-clause (polite question)

Elena asked if anyone knew the fastest way to the train station.

know + if-clause in reported speech

Common collocations
  • do you know...?
  • anyone know...?
  • wondering if you know
Synonyms
  • find out

    focuses on the act of discovering, not just asking

  • learn

    implies receiving new information, not requesting known facts

Grammar Patterns

Do you know + wh-clause?

know + if/whether

Usage Note

Used mainly in questions ('Do you know…?') and reported speech ('She asked if I knew…'). The focus is on requesting information, not stating that you have it.

Common Mistakes

Do you know where is the station?
Do you know where the station is?
In embedded wh-questions, the subject comes before the verb, unlike in direct questions.

3. to feel completely sure about something, without any doubt in your mind.

3.verbtransitive / intransitiveA2
Definition

to feel completely sure about something, without any doubt in your mind.

Example

Eitan knew for sure that he had locked the front door before leaving.

know for sure + that-clause

I do not know if this bus goes all the way to the airport.

know + if-clause (uncertainty)

Common collocations
  • know for sure
  • know for certain
  • know full well
  • know in your heart
Synonyms
  • be certain

    interchangeable in most contexts; 'certain' is slightly more formal

  • be convinced

    stronger; implies you have considered arguments or evidence

  • be positive

    informal; very strong degree of certainty

Antonyms
  • doubt

    the opposite feeling — you think something may not be true

  • be unsure

    milder than doubt; means you have not yet decided

Grammar Patterns

know + that-clause

know + for sure / for certain

I know (intransitive, as response)

Usage Note

Often used with 'that-clause' or modifiers like 'for sure' and 'for certain'. The negative form ('I don't know if…') expresses uncertainty — distinguish from sense 1 (lacking factual information).

Common Mistakes

I know for sure that he will coming.
I know for sure that he will come.
The verb after 'will' must stay in base form.

4. to have met a person, visited a place, or used a thing often enough to feel comf

4.verbtransitiveA1
Definition

to have met a person, visited a place, or used a thing often enough to feel comfortable with them.

Example

Yuna knows the owner of the small coffee shop on the corner.

know + person

The Chen family has known our neighbours for more than ten years.

know + person (past participle, duration)

Common collocations
  • know someone well
  • know a place like the back of your hand
  • get to know
  • know by name
  • know by sight
Synonyms
  • be acquainted with

    more formal; often used in introductions ('pleased to make your acquaintance')

  • be familiar with

    can apply to places and things; slightly more formal than 'know'

Antonyms

Grammar Patterns

know + person

know + place

know + thing

Usage Note

Distinguish from sense 1: sense 4 is about personal acquaintance or familiarity through experience, not about having facts in your mind. You can 'know a person' without 'knowing their phone number' (sense 1).

Common Mistakes

I know him for five years.
I have known him for five years.
With durations, use the present perfect, not the simple present.

5. to have learned a subject, skill, or topic well enough to understand and talk ab

5.verbtransitiveB1
Definition

to have learned a subject, skill, or topic well enough to understand and talk about it.

Example

Owen knows computer programming better than anyone else in the class.

know + subject (comparative)

Tariro knows a lot about how modern car engines actually work.

know about + topic

Common collocations
  • know how to
  • know a lot about
  • know inside out
  • know backwards and forwards
Synonyms
  • understand

    implies deeper comprehension; 'understand' can be used where 'know' feels too shallow

  • have mastered

    stronger; suggests complete, expert-level knowledge

  • be versed in

    formal; suggests studied knowledge of a field

Antonyms

Grammar Patterns

know + subject / field of study

know + how + infinitive

Usage Note

Commonly used with 'how + infinitive' for practical skills ('know how to fix a bike'). The object is typically a field, topic, or skill — not a person or place.

Common Mistakes

I know to swim.
I know how to swim.
For skills and abilities, you must use 'know how to', not 'know to'.

6. to be able to speak, read, and understand a particular language.

6.verbtransitiveA2
Definition

to be able to speak, read, and understand a particular language.

Example

Caio knows three languages, including Japanese and Mandarin Chinese.

know + number + languages

Do you know enough Spanish to order food and ask for directions?

know + language + enough (sufficiency)

Common collocations
  • know a language
  • know some French
  • know a little German
  • know enough English
Synonyms
  • speak

    focuses on oral ability, while 'know' includes reading and writing too

  • be fluent in

    stronger; suggests a high level of proficiency

Antonyms
  • not speak

    direct opposite — you cannot use the language at all

Grammar Patterns

know + language

Usage Note

This sense only takes languages as objects ('know French', 'know Japanese'). Do not confuse with sense 5, which takes subjects or topics ('know physics', 'know history').

Common Mistakes

I know to speak Korean.
I know Korean.' or 'I can speak Korean.
When talking about languages, use 'know + language name directly, not 'know to speak + language'.

7. to identify a person, thing, or sound that you have seen or heard before.

7.verbtransitiveB1
Definition

to identify a person, thing, or sound that you have seen or heard before.

Example

Ada knew the song the moment she heard the first few notes.

know + noun phrase for recognizing

From a single childhood photograph, the officer knew the suspect years later.

Common collocations
  • know by sight
  • know by name
  • know from somewhere
Synonyms
  • recognize

    focused on the act of identifying rather than the state of familiarity

  • place

    informal; means you connect a face or name to a specific context

  • identify

    more formal; often used for official or technical recognition

Grammar Patterns

know + noun phrase

Usage Note

Frequently used with a sensory cue (voice, smell, sight) that triggers recognition.

Common Mistakes

I knew him yesterday at the station.
I recognized him yesterday at the station.
'know' is a stative verb; for an event of identification, use 'recognize'.

8. to have learned the knowledge or skill needed to do something.

8.verbtransitive / intransitiveA2
Definition

to have learned the knowledge or skill needed to do something.

Example

Vikram knows how to change a flat tyre in under ten minutes.

know + how + to-infinitive for practical ability

My grandmother knows how to make traditional Korean kimchi from scratch every autumn.

Common collocations
  • know how to
  • know what to
  • know where to
Synonyms
  • can

    more direct; expresses ability without specifying the underlying knowledge

  • be able to

    more formal; emphasises capability rather than learned knowledge

Grammar Patterns

know + how/what/where/ when + to-infinitive

Usage Note

The most common pattern is 'know how to' + base verb. 'Know what to' and 'know where to' are also frequent. This sense is stative and rarely used in progressive tenses ('*I am knowing how to do it').

Common Mistakes

I know to swim.
I know how to swim.
'know' + bare to-infinitive is not correct English; you need 'how to'.

9. to become familiar with a person, place, or thing through experience over time.

9.verbtransitiveB1
Definition

to become familiar with a person, place, or thing through experience over time.

Example

Moving to a new city meant getting to know a completely different neighbourhood.

get to know + noun phrase for gradual familiarisation

The first few weeks at the job were all about knowing the company culture.

Common collocations
  • get to know
  • know well
  • know inside out
Synonyms

Grammar Patterns

get to know + noun phrase

know + noun phrase

Usage Note

The phrasal form 'get to know' emphasises the gradual process of becoming familiar, while plain 'know' describes the resulting state. Frequently used with places, cultures, and people.

Common Mistakes

I am knowing her better every day.
I am getting to know her better every day.
'know' is stative and does not take progressive forms; use 'get to know' for an ongoing process.

10. to be aware of a person or thing by reputation but without knowing them directly

10.verbtransitiveB1
Definition

to be aware of a person or thing by reputation but without knowing them directly.

Example

Karim had heard of the author but did not know any of his books well.

know of + noun phrase for familiarity by reputation only

I know of Dr Chen from the university newsletter, though we have never met.

Common collocations
  • know of
  • heard of
Synonyms
  • have heard of

    more explicit about the auditory source of the information

  • be aware of

    broader; can refer to facts, events, or abstract concepts

Antonyms
  • know

    direct familiarity as opposed to second-hand awareness

Grammar Patterns

know of + noun phrase

Usage Note

Commonly expressed as 'know of' (aware of existence without direct familiarity). Distinguish from sense 7 (RECOGNIZE) which involves personal recognition, and sense 12 (BY SIGHT) which involves visual familiarity.

Common Mistakes

I know of him personally.
I know him personally.
'know of' means you have heard about someone but do not know them directly; adding 'personally' contradicts the meaning.

11. to be slightly familiar with a person, for example by knowing their name but not

11.verbtransitiveB2
Definition

to be slightly familiar with a person, for example by knowing their name but not knowing them well.

Example

Christopher knows several people in the building by name but rarely stops to chat.

know + by name for slight acquaintance

The shopkeeper and I know each other by a nod, but have never talked.

Common collocations
  • know by name
  • know slightly
  • know to say hello to
Synonyms
Antonyms

Grammar Patterns

know + noun phrase

Usage Note

This sense describes a relationship that is more than 'knowing of' (sense 10) but less than close friendship. Subject is often a person or a group. Common with 'know someone by name' or 'know someone to say hello to'.

Common Mistakes

I know her for many years.
I have known her for many years.
'know' in this sense still follows stative verb rules; use present perfect for duration.

12. to recognize a person by their appearance without knowing their name or having m

12.verbtransitiveB1
Definition

to recognize a person by their appearance without knowing their name or having met them.

Example

The security guard knows the office workers by sight but does not know their names.

know + by sight for visual recognition without personal acquaintance

The woman at the park is familiar by sight, but we have never spoken.

Common collocations
  • know by sight
  • familiar by sight
Synonyms

Grammar Patterns

know + noun phrase + by sight

Usage Note

Almost always occurs with the fixed phrase 'by sight'. Distinguish from sense 7 (RECOGNIZE) where you can identify a specific person or thing you already know, and from sense 11 (ACQUAINTANCE) where you also know the person's name.

Common Mistakes

I know her by the sight.
I know her by sight.
no article; 'by sight' is a fixed expression.
Idioms

before you know where you are

idiom

Used to say that something happens very quickly or suddenly.

The kids grow up before you know where you are.

Before you know where you are, the summer will be over.

be not to know

idiom

Used to say that someone had no way of realizing they did something wrong.

Don't blame him for the mistake; he was not to know.

I'm sorry I broke the vase. You weren't to know it was fragile.

better the devil you know (than the devil you don’t)

idiom

Used to say that it is safer to stay in a bad situation you are used to than to change to a new one that might be worse.

I stayed in my old job because better the devil you know.

She decided not to move; better the devil you know, she thought.

for all you, I, they, etc. know

idiom

Used to emphasize that you do not know something and it does not matter to you.

For all I know, he could be living in Paris now.

She might have already left, for all we know.

God/goodness/Heaven knows

idiom

Used to emphasize that you do not know something or to show surprise.

God knows where she put the keys.

Goodness knows why he said that.

have/know all the answers

idiom

To be too confident that you know everything, especially when you actually do not.

He thinks he knows all the answers, but he's often wrong.

Don't act like you have all the answers; listen to others.

have/know something off pat

idiom

To know something perfectly so you can repeat it without thinking.

She had her speech off pat after practicing all week.

The actor knew his lines off pat for the audition.

have seen/known better days

idiom

To be in poor condition, usually because of age or use.

This old sofa has seen better days.

My car has known better days; it's falling apart.

I don’t know how, why, etc…

idiom

Used to criticize someone's behavior by saying you cannot understand it.

I don't know how you can eat that spicy food.

I don't know why she would lie about such a small thing.

if (the) truth be known/told

idiom

Used to tell someone the true facts, especially when others do not know them.

If truth be told, I was nervous about the exam.

If the truth be known, she never liked the gift.

I know

idiom

Used to agree with someone or show sympathy.

This traffic is terrible. I know, it's so frustrating.

I know, let's order pizza for dinner tonight.

know something as well as I do

idiom

Used to criticize someone by saying they should already realize something.

You know as well as I do that we can't afford a new car.

She knows as well as I do that the deadline is tomorrow.

know somebody/something backwards

idiom

To know someone or something extremely well.

After ten years, she knows the company backwards.

He knows the city backwards, so he's a great tour guide.

know best

idiom

To know what should be done better than other people.

My mother always thinks she knows best about my life.

The coach knows best, so follow his instructions.

know somebody by sight

idiom

To recognize someone without knowing them personally.

I know the new neighbor by sight, but we've never spoken.

She knows the actor by sight from seeing his movies.

know different/otherwise

idiom

To have information that proves the opposite of what someone says is true.

He claims he's innocent, but I know different.

She says the store is closed, but I know otherwise.

know full well

idiom

To be very aware of a fact and unable to deny it.

He knew full well that lying would get him in trouble.

She knew full well the test was today, yet she didn't study.

know your own mind

idiom

To have clear and definite ideas about what you want.

Even as a child, she knew her own mind and spoke it.

He knows his own mind when it comes to career choices.

know your stuff

idiom

To know a lot about a particular subject or job.

Our tour guide really knows his stuff about ancient history.

She knows her stuff when it comes to fixing cars.

know/learn/find something to your cost

idiom

To know something because of an unpleasant experience you had.

He learned to his cost that investing in risky stocks is dangerous.

I know to my cost that skipping meals leads to headaches.

know your way around

idiom

To be familiar with a place, subject, or system.

After a week, she knew her way around the new office.

He knows his way around computer programming.

know what you’re talking about

idiom

To have knowledge about something from personal experience.

I've been a teacher for 30 years, so I know what I'm talking about.

She knows what she's talking about when it comes to baking.

know which side your bread is buttered

idiom

To know where you can get an advantage for yourself.

He always flatters the boss; he knows which side his bread is buttered.

She knows which side her bread is buttered, so she never argues with clients.

let it be known/make it known that…

idiom

To make sure people are informed about something, often through someone else.

The manager let it be known that the office would close early on Friday.

She made it known that she was looking for a new job.

let somebody know

idiom

To tell someone something.

Please let me know if you need any help with the project.

Let us know when you arrive at the station.

Lord knows…

idiom

Used to emphasize what you are saying.

Lord knows, I've tried my best to help him.

Lord knows, she deserves a break after all that work.

make yourself known to somebody

idiom

To introduce yourself to someone.

When you arrive, make yourself known to the receptionist.

He made himself known to the new neighbors at the party.

not know any better

idiom

To behave badly because you have not been taught the correct way.

The child didn't know any better and took the toy without asking.

Don't be angry at the puppy; it doesn't know any better.

not know your arse from your elbow

idiom

To be very stupid or have no skill at all.

He can't even change a tire; he doesn't know his arse from his elbow.

She doesn't know her arse from her elbow when it comes to math.

not know beans about something

idiom

To know nothing about a subject.

I don't know beans about fixing computers.

She doesn't know beans about cooking Italian food.

not know somebody from Adam

idiom

To not know who someone is at all.

I've never met him; I don't know him from Adam.

She claims she knows me, but I don't know her from Adam.

not know what hit you

idiom

To be so surprised by something that you do not know how to react.

When he won the lottery, he didn't know what hit him.

The sudden news left her not knowing what hit her.

not know where to look

idiom

To feel very embarrassed and not know how to react.

When he spilled coffee on the boss, he didn't know where to look.

She was so embarrassed she didn't know where to look.

not know whether you’re coming or going

idiom

To be so confused or busy that you cannot think clearly.

With all these deadlines, I don't know whether I'm coming or going.

She was so excited she didn't know whether she was coming or going.

not know you are born

idiom

To have an easy life without realizing how easy it is.

Kids today don't know they are born with all this technology.

He complains about his job, but he doesn't know he's born.

not want to know (about something)

idiom

To take no interest in something because you do not care or it is too much trouble.

I tried to explain, but she didn't want to know.

How much did it cost? You don't want to know.

old enough to know better

idiom

Old enough to behave in a more sensible way than you did.

He's 15, old enough to know better than to throw rocks.

She's old enough to know better than to stay out late.

show somebody/know/learn the ropes

idiom

To show someone, know, or learn how a job is done.

The senior employee showed the new hire the ropes.

It took me a month to learn the ropes at the new company.

there’s no knowing

idiom

Used to say that it is impossible to say what might happen.

There's no knowing what the weather will be like tomorrow.

There's no knowing how he will react to the news.

what does… know?

idiom

Used to say that someone knows nothing about the subject.

What does he know about cooking? He can't even boil an egg.

What does she know about cars? She's never driven one.

what do you know?

idiom

Used to express surprise.

Well, what do you know? It's actually sunny today!

What do you know? She won the race after all.

(know) what’s what

idiom

To know what things are useful, important, or true.

After years in the business, she knows what's what.

He doesn't know what's what when it comes to fashion.

you know

idiom

Used when you are thinking of what to say next or to refer to something already known.

It's, you know, hard to explain in just a few words.

You know that café on the corner? It's closed now.

you know something/what?

idiom

Used to introduce an interesting or surprising opinion or news.

You know something? I've never actually seen that movie.

You know what? I think we should go on a trip.

you know who/what

idiom

Used to refer to someone or something without mentioning a name.

I saw you know who at the mall yesterday.

She told me about you know what, but I can't say more.

you never know

idiom

Used to say that you can never be certain about the future, especially when something good might happen.

You never know, you might win the lottery someday.

Apply for the job; you never know, they might hire you.

know — noun

Word family

Synonym discussion

Sense: verb/1

「know」（知道）是最基礎的用詞，指腦中儲存了事實或資訊，屬於狀態動詞。相較之下，「understand」（理解）強調的不僅是知道事實，還包括掌握其中的道理、因果關係或運作方式——例如「I know the rules」（我知道規則）只是能背出規則，而「I understand the rules」（我理解規則）則代表能運用規則。「comprehend」（領悟）比 understand 更正式且程度更深，常用於抽象或複雜的概念，如「comprehend the theory of relativity」（領悟相對論）。「recognize」（辨認、認出）則側重於從過往經驗中再次識別出來，通常伴隨視覺、聽覺等感官線索——例如「I know her name」（我知道她的名字）與「I recognized her face」（我認出了她的臉）之間的差異。簡單來說：know 是「知道」，understand/comprehend 是「理解」，recognize 是「認出」。在學術寫作中，understand 與 comprehend 較常出現；日常對話則多用 know 與 recognize。

understand ↗comprehendrecognize ↗

Common collocations

Verbs

  • get to know
  • come to know
  • let know
  • make known

Adverbs

Phrases

Prepositions

Etymology

Proto-Indo-EuropeanProto-GermanicOld EnglishMiddle EnglishModern English

「know」源自古英語「cnāwan」，意為「知道、認識」。追溯至原始日耳曼語「*knēaną」，再遠溯至原始印歐語「*ǵneh₃-」（知道）。同源詞包括拉丁語「gnoscere」（知道，英語「recognize」由此而來）、希臘語「gignōskein」（知道，「gnosis」一詞由此而來），以及梵語「jñā-」（知道）。現代英語中，「know」涵蓋了事實認知、技能熟悉、人際認識等廣泛義項。