#1 – as far as I know
Use this expression to say that you believe a fact is true… although there is a possibility that you could be mistaken.
“As far as I know, the museum opens at 8. But you might want to call to make sure.”
#2 – before you know it
This expression means something will happen so soon, it will be surprising. It’s often used to talk about events coming up in the future, when time seems to pass quickly.
“Enjoy your day at the beach! The summer will be over before you know it.”
It’s also possible to say “before I knew it” when something happened surprisingly quickly in the past:
“I opened the door just a bit, and before I knew it, the dog had run past me and gotten out of the house.”
#3 – not know what to make of something
This means you are not sure how to interpret something, or what it means.
Reacting to something someone said:
“I thought our relationship was going really well, so I don’t know what to make of her request to give her ‘more space.'”
Reacting to an action:
“I don’t know what to make of the company’s decision to discontinue one of the most popular products. It seems like they just don’t care about the customers anymore.”
#4 – not know the first thing about
If somebody doesn’t know the first thing about something, it means they know absolutely nothing about it; they are completely unfamiliar with it.
“I don’t know the first thing about how to fix a car engine. I’ll have to call the mechanic.”
#5 – dying to know
If you are “dying to know” something, it means you have a VERY strong desire to know:
“My best friend says she’s planned a really great surprise for my birthday… I’m dying to know what it is!”
#6 – God only knows
This expression means that nobody knows something. It can be used as part of a sentence, or as a response to a question:
As part of a sentence:
“God only knows how many people have died due to lack of clean water.”
As a response to a question:
“We’ve been waiting in line for five hours. How much longer is this going to take?”
“God only knows!”
#7 – if you know what’s good for you
This expression is used as a threat – saying that somebody should definitely do something; if they don’t, they will be in trouble.
“Hey man, you’d better stay away from my girlfriend if you know what’s good for you!” (implying that there will be a fight if the other guy does not stay away from the girlfriend)
#8 – know backwards and forwards /
know inside out
Both of these expressions are used for when you know something extremely well; you know almost everything there is to know about the topic or area.
“He’s been teaching physics for 35 years; he knows the subject backwards and forwards.”
“Of course I know this equipment inside out – I was the one who designed it.”
#9 – know beyond a shadow of a doubt
Use this expression when you have 100% certainty that a fact is true.
“We know beyond a shadow of a doubt that he stole the documents – the video camera filmed him doing it!”
#10 – know by heart
This expression means you have memorized something perfectly.
“This is my favorite song. I know all the lyrics by heart!“