A1 to have information about something in your mind: Andrew knows a lot about cars. “How old is she?” “I don’t know.” He knew that she was lying.
A1 used to ask someone to tell you a piece of information: Do you know where the post office is?
A2 to be certain: I know she’ll be really pleased to hear the news.
A2 to be able to do something: Do you know how to ski?
B1 to have spent time with someone or in a place so that the person or place is not new to you: I’ve known Al since we were children. I grew up in Boston, so I know it well.
let someone know A2 to tell someone something: Let me know if you’re going to the party.
I know › used when you agree with something someone has just said: “It’s a beautiful day, isn’t it?” “I know – let’s hope it lasts.”
you know B1 used to make sure someone understands which person or thing you are talking about: I was talking about Rachel – you know, the tall woman with the blond hair.
B1 (also know about) If you know a subject, you are familiar with it and understand it: Ask Andy to fix it – he knows about computers.
be known as something B1 to be called: California is also known as the Sunshine State.
get to know someone/something B1 to gradually learn more about someone or something: I got to know Frank at work.
as far as I know › used to say that you think something is true, but cannot be sure: As far as I know, he isn’t married.