As we know it
This is an expression used when you are talking about something people are familiar with, especially something that is likely to change forever.
- A nuclear war could mean the end of the world as we know it.
As you know
This expression is used when you are saying something that somebody already knows.
- As you know, we have already discussed this.
Get to know = start to be familiar with someone or something
- She is nice when you get to know her.
- It took me a while to get to know the city properly.
This is an expression used for saying that you do not know something.
- ‘Where on earth is he at the moment?’ ‘Goodness knows.’
I don’t know
This expression is sometimes used for saying that you do not completely agree.
- ‘I think the film will be boring.’ ‘Oh I don’t know. It could be interesting.’
This expression can also be used for criticizing people.
- I don’t know how people can be so insensitive.
If you must know
This is an expression used when you are answering someone in an annoyed way.
- I’m not seeing him, if you must know.
- He is not my boyfriend, if you must know.
Know something backwards / know something inside out
When you know something inside out / backwards you are very familiar with it.
- When it comes to toys, children know best.
- When it comes to cosmetics, women know best.
When you know better you know that what someone says or does is wrong.
- Everybody thought that it was an innocent prank, but I knew better. (= I knew that it was not an innocent mistake.)
Know your own mind
When you know your own mind you are certain about what you like and what you want.
- Francis has always been a man who knows his own mind.
Know what’s what
To know what’s what is to be very clever or experienced.