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Definition of know verb from the Oxford Advanced American Dictionary

Oxford3000

know

verb
/noʊ/ know pronunciation American
 
knew
/nu/ knew pronunciation American
, known
/noʊn/ known pronunciation American
(not used in the progressive tenses)

have information

1 [transitive, intransitive] to have information in your mind as a result of experience or because you have learned or been told it know somethingDo you know his address?The cause of the fire is not yet known.All I know is that she used to work in a bank (= I have no other information about her). know (that)…I know (that) people's handwriting changes as they get older. it is known that…It is widely known that CFCs can damage the ozone layer. know where, what, etc.…I knew where he was hiding.I didn't know what he was talking about. know (of/about something)“You've got a flat tire.” “I know.”“What's the answer?” “I don't know.”“There's no one home.” “ How do you know?You know about Amanda's baby, don't you?I don't know about you, but I'm ready for something to eat.I know of at least two people who did the same thing.“Is anyone else coming?” “ Not that I know of.“Isn't that his car?” “ I wouldn't know./How should I know?(= I don't know and I am not the person you should ask).(informal)“What are you two whispering about?” “ You don't want to know.” (= because you would be shocked or wouldn't approve) know to do somethingDoes he know to come here (= that he should come here) first? know someone/something to be/do somethingWe know her to be honest.Two women are known to have died. see also need-to-know

realize

2 [transitive, intransitive] to realize, understand, or be aware of something know (that)…As soon as I walked in the room I knew (that) something was wrong.She knew she was dying. know what, how, etc.…I knew perfectly well what she meant.I know exactly how you feel. know (something)This case is hopeless and he knows it (= although he will not admit it).“Martin was lying the whole time.” “ I should have known.”

feel certain

3 [transitive, intransitive] to feel certain about something know (that)…He knew (that) he could trust her.I know it's here somewhere!I know things will turn out all right.I don't know that I can finish it by next week.I just knew that it was something I wanted to do. know (something)“You were right—someone's been spreading rumors about you.” “I knew it!”“She's the worst player in the team.” “Oh, I don't know (= I am not sure that I agree) —she played well yesterday.”

be familiar

4 [transitive] know someone/something to be familiar with a person, place, thing, etc.I've known David for 20 years.Do you two know each other (= have you met before)?She was a secretary when I first knew her.She's very nice when you get to know her.Knowing Ben, we could be waiting a long time (= it is typical of him to be late).This man is known to the police (= as a criminal).I don't know anyone in Albuquerque.I know Savannah well.Do you know the play (= have you seen or read it before)?The new rules could mean the end of football as we know it (= in the form that we are familiar with).

reputation

5 [transitive, usually passive] to think that someone or something is a particular type of person or thing or has particular characteristics know someone/something as somethingIt's known as the most dangerous part of the city. know someone/something for somethingShe is best known for her work on the human brain. know someone/something to be/do somethingHe's known to be an outstanding physicist.

give name

6 [transitive] know someone/something as something [usually passive] to give someone or something a particular name or titleAscorbic acid is more commonly known as Vitamin C.Peter Wilson, also known as “the Tiger.”

recognize

7 [transitive] know someone/something to be able to recognize someone or somethingI couldn't see who was speaking, but I knew the voice.She knows a bargain when she sees one.

distinguish

8 [transitive] know someone/something from someone/something to be able to distinguish one person or thing from another synonym differentiateI hope we have taught our children to know right from wrong.

skill/language

9 [transitive] to have learned a skill or language and be able to use it know somethingDo you know any Japanese? know how, what, etc.…Do you know how to use spreadsheets?

experience

10 [transitive] (only used in the perfect tenses) to have seen, heard, or experienced something know someone/something (to) do somethingI've never known it (to) snow in July before. be known to do somethingHe has been known to spend all morning in the bathroom.11 [transitive] know something to have personal experience of somethingHe has known both poverty and wealth.She may be successful now, but she has known what it is like to be poor.
IDIOMS

as far as I know

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as far as I can remember, see, tell, etc.

used to say that you think you know, remember, understand, etc. something but you cannot be completely sure, especially because you do not know all the facts
As far as we knew, there was no cause for concern.As far as I can see, you haven't done anything wrong.She lived in Chicago, as far as I can remember.as far as I know

before you know where you are

very quickly or suddenly
We were whisked off in a taxi before we knew where we were.before you know where you are

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

(saying) used to say that it is easier and wiser to stay in a bad situation that you know and can deal with rather than change to a new situation that may be much worsebetter the devil you knowbetter the devil you know than the devil you don't

for all you, I, they, etc. know

(informal) used to emphasize that you do not know something and that it is not important to youShe could be dead for all I know.for all you, I, they, etc. know

God/goodness/Heaven knows

(informal)1 used to emphasize that you do not know somethingGod knows what else they might find.“Where are they?” “Goodness knows.”help Some people may find the use of God knows offensive.2 used to emphasize the truth of what you are sayingShe ought to pass the exam—goodness knows she's been working hard enough.God/Heaven knowsgoodness/Heaven knows

have/know all the answers

(informal, often disapproving) to be confident that you know something, especially when you actually do notHe thinks he knows all the answers.have all the answersknow all the answers

have/know something down pat

to know something perfectly so that you can repeat it at any time without having to think about it
He had all the answers down pat.have down patknow down pat

have seen/known better days

(humorous) to be in poor conditionOur car has seen better days!have seen better dayshave known better days

I don't know how, why, etc.…

(informal) used to criticize someone's behaviorI don't know how you can say things like that.I don't know how, why, etc.

if (the) truth be known/told

used to tell someone the true facts about a situation, especially when these are not known by other people
if truth be knownif the truth be knownif truth be toldif the truth be told

I know

(informal)1 used to agree with someone or to show sympathy“What a ridiculous situation!” “I know.”2 used to introduce a new idea or suggestionI know, let's see what's playing at the theater.I know

know something as well as I do

used to criticize someone by saying that they should realize or understand something
You know as well as I do that you're being unreasonable.know as well as I do

know someone/something backward and forward

(informal) to know someone or something extremely wellShe must know the play backward and forward by now.know backward and forward

know best

to know what should be done, etc. better than other people
The doctor told you to stay in bed, and she knows best.know best

know better (than that/than to do something)

to be sensible enough not to do something
He knows better than to judge by appearances.know betterknow better than that to doknow betterknow better than than to do

know someone by sight

to recognize someone without knowing them well
know by sight

know different/differently/otherwise

(informal) to have information or evidence that the opposite is trueHe says he doesn't care about what the critics write, but I know different.know different/otherwiseknow differently/otherwise

know full well

to be very aware of a fact and unable to deny or ignore it
He knew full well what she thought of it.know full well

know someone/something inside out

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know someone/something like the back of your hand

(informal) to be very familiar with somethingThis is where I grew up. I know this area like the back of my hand.know inside out

know your own mind

to have very firm ideas about what you want to do
know your own mind

know your stuff

(informal) to know a lot about a particular subject or jobknow your stuff

know/tell someone a thing or two (about someone/something)

(informal) to know/tell someone some useful, interesting, or surprising information about someone or somethingShe's been married five times, so she knows a thing or two about men!know a thing or twoknow a thing or two abouttell a thing or twotell a thing or two about

know your way around

to be familiar with a place, subject, etc.
know your way around

know what you're talking about

(informal) to have knowledge about something from your own experienceI've lived in China, so I know what I'm talking about.know what you're talking about

know which side your bread is buttered (on)

(informal) to know where you can get an advantage for yourselfknow which side your bread is butteredknow which side your bread is buttered on

let it be known/make it known that…

(formal) to make sure that people are informed about something, especially by getting someone else to tell themThe President has let it be known that he does not intend to run for re-election.let it be known it known thatlet it be make it known that

let someone know

to tell someone about something
I don't know if I can come, but I'll let you know tomorrow.Let me know how I can help.let know

Lord knows…

used to emphasize what you are saying
Lord knows, I tried to teach her.Lord knows

Lord (only) knows (what, where, why, etc.)…

(informal) used to say that you do not know the answer to something“Why did she say that?” “Lord knows!”Lord knowsLord only knows what, where, why, etc.

make yourself known to someone

to introduce yourself to someone
I made myself known to the hotel manager.make yourself known to

not know any better

to behave badly, usually because you have not been taught the correct way to behave
Don't blame the children—they don't know any better.not know any better

not know beans about something

(informal) to know nothing about a subjectI don't know beans about making movies.not know beans about

not know the first thing about someone/something

to know nothing at all about someone or something
I'm afraid I don't know the first thing about cars.not know the first thing about

not know, etc. the first thing about something/someone

to know nothing at all about something or someone
We've lived next to him for years, but we still don't know the first thing about him.not know, etc. the first thing about

not know someone from Adam

(informal) to not know at all who someone isnot know from Adam

not know what hit you

(informal) to be so surprised by something that you do not know how to reactnot know what hit you

not know where to look

(informal) to feel great embarrassment and not know how to reactnot know where to look

not know whether you're coming or going

(informal) to be so excited or confused that you cannot behave or think in a sensible waynot know whether you're coming or going

old enough to know better

old enough to behave in a more sensible way than you actually did
old enough to know better

show someone/know/learn the ropes

(informal) to show someone/know/learn how a particular job should be doneshow/learn the ropesshow know/learn the ropes

there's no knowing

used to say that it is impossible to say what might happen
There's no knowing how he'll react.there's no knowing

what does… know?

used to say that someone knows nothing about the subject you are talking about
What does he know about football, anyway?what does know?

what do you know?

(informal) used to express surpriseWell, what do you know? Look who's here!what do you know?

you know

(informal)1 used when you are thinking of what to say nextWell, you know, it's difficult to explain.2 used to show that what you are referring to is known or understood by the person you are speaking toGuess who I've just seen? Maggie! You know—Jim's wife.You know that restaurant around the corner? It's closing down.3 used to emphasize something that you are sayingI'm not stupid, you know.you know

you know something/what?

(informal) used to introduce an interesting or surprising opinion, piece of news, etc.You know something? I've never really enjoyed Christmas.you know something?you know what?

you know who/what

(informal) used to refer to someone or something without mentioning a nameyou know whoyou know what

you never know

(informal) used to say that you can never be certain about what will happen in the future, especially when you are suggesting that something good might happenyou never know
Usage notesThesaurus: identifyknow recognize name make someone/something outThese words all mean to be able to see or hear someone or something and especially to be able to say who or what they are.identify to be able to say who or what someone or something is: He was able to identify his attacker.know to be able to say who or what something is when you see or hear it because you have seen or heard it before note Know is used especially to talk about sounds that seem familiar and when someone recognizes the quality or opportunity that someone or something represents: I couldn't see who was speaking, but I knew the voice. She knows a bargain when she sees one.recognize to know who someone is or what something is when you see or hear them/it, because you have seen or heard them/it before: I recognized him as soon as he came into the room.name to say the name of someone or something in order to show that you know who/what they are: The victim has not yet been named in the newspapers.make someone/something out to manage to see or hear someone or something that is not very clear: I could just make out a figure in the darkness.patternsto identify/know/recognize someone/something by somethingto identify/recognize/name someone/something as someone/somethingto identify/know/recognize/make out who/what/how…to easily/barely/just identify/recognize/make out someone/something