be on the ball

If you are on the ball, you are aware of what is happening and are able to deal with things quickly and intelligently.
“We need someone who is really on the ball to head the fund-raising campaign.”

beat one’s brains out

If someone beats their brains out, they try very hard to understand something or solve a problem.
“My grandmother beats her brains out every evening trying to do the crossword puzzle in the newspaper.”

it beats me!

This expression is used to express surprise at something that you find difficult to understand.
It beats me how he can live in that horrible apartment!”

it’s beyond me

To say ‘it’s beyond me’ means that it is impossible for you to understand.
It’s beyond me why Mary wants to marry John.”

blind you with science

If someone tries toblind you with science, they confuse you with their knowledge by using difficult or technical words.
“When you ask Tim for a simple explanation, he blinds you with science.”

I wasn’t born yesterday

This expression is used to indicate that you are not as foolish or as easily deceived as some people seem to think.
“Stop inventing silly excuses. I wasn’t born yesterday you know!”

(the) brains behind something

Someone who is the brains behind a project or action is the person thought to have planned and organised everything.
“The police have arrested a man believed to be the brains behind the bank robbery.”

can’t make head or tail of (something)

If you can’t make head or tail of something, you can’t understand it at all.
“Amy’s message was so confusing. I couldn’t make head or tail of it!”

put on your thinking cap

If you tell someone to put their thinking cap on, you ask them to find an idea or solve a problem by thinking about it.
“Now here’s this week’s quiz; it’s time to put your thinking caps on!”

chinese arithmetic

If something is very complicated or difficult to understand, it is said to be like Chinese arithmetic.
“When he tried to explain the rules of the game to me, it was like Chinese arithmetic!”

not have a clue

If you don’t have a clue about something, you don’t know anything about it.
“My wife’s grandmother’s maiden name? I don’t have a clue!

collect one’s thoughts

If you collect your thoughts, you try to think calmly and clearly in order to prepare yourself mentally for something.
“Anne stopped to collect her thoughts before calling back the customer.”

come to grips with

If you come to grips with a problem or situation, you start to understand or deal with it properly.
“After the initial shock, the patient began to come to grips with his disability.”

come to your senses

If you come to your senses you start to think clearly and behave sensibly.
“She finally came to her senses and realized that public transport was faster than driving in the city.”

common knowledge

When information is well-known to everyone (particularly in a community or group), it is called common knowledge.
“You didn’t know the intern was Jack’s son? It thought it was common knowledge.”

credibility gap

The extent of disbelief, of the difference between what you are asked to believe and what you are able to believe, is call a credibility gap.
“The growing credibility gap may lead to a serious loss of votes in the next elections.”

at cross purposes

If two people areat cross purposes, there is a misunderstanding as to what each one is talking about.
“Look, we seem to be at cross purposes. You’re talking about ‘sailing’ boats, but I’m talking about ‘selling’ boats.”

crystal clear

A statement or expression that is easy to understand or has an obvious meaning is crystal clear
“There’s no need to repeat the instructions. They were crystal clear.”

dumbing down

If something, such as a television programme or a film production, is dumbed down, it is deliberately made less intelligent or less demanding in order to attract a larger audience.
“Some TV channels are dumbing down their programmes in an attempt to increase their audience ratings.”

enough said

This expression is used to indicate that you completely understand the situation and you do not need any further details.
“Your mother-in-law arrived unexpectedly last night? Enough said!”

eyes (wide) open

If you do somethingwith your eyes open, you are fully aware of what you are doing.
“I took on the job with my eyes wide open so I’m not complaining”

facts speak for themselves

When the facts of a situation are co clear that no further explanation or extra details are necessary, the facts speak for themselves.
“No need to tell you that the situation is disastrous. The facts speak for themselves.”

get someone’s drift

If you get someone’s drift, you understand in a general way what they are trying to say.
“I didn’t understand every word but I got the drift.”

get the message

If you get the message, you understand what someone is trying to tell you, even if it is expressed in actions or gestures rather than words.
“When Tony pointed to his watch, I got the message – it was time to leave for the airport.”

get the picture

A person who gets the picture understands what is being explained or described.
“The alarm went off and people started running everywhere – you get the picture I’m sure!”

(it’s all) greek to me!

This expression means that you do not understand what is being said or written or that you find it incomprehensible.
“He showed us a complex diagram to illustrate his idea but it was all greek to me!”

get wise to something

If you get wise to something, you learn something that you were not aware of before.
“The old man finally got wise to the fact that children were stealing apples from his garden.”

go over your head

If something said or written goes over your head, you find it too difficult to understand or follow.
“I always found mathematics difficult at school. The teacher’s explanations just went over my head!”

hammer something home

If you hammer home a point or an argument, you repeat it often to make sure that it is fully understood.
“The police hammered home the dangers of drinking and driving.”

hit the nail on the head

When you hit the nail on the head, you are absolutely right about something or have guessed the exact nature of a problem or situation.
“You hit the nail on the head when you said Mark had money problems. He’s lost his job.”

horse sense

Someone who has horse sense is a practical thinker who has the ability to make sensible decisions.
“Don’t worry. Andrew has good horse sense. He’ll do the right thing.”

ignorance is bliss

To say ‘ignorance is bliss’ means that if you don’t know about a problem or unpleasant fact, you won’t worry about it.
“I didn’t know our neighbour was an escaped prisoner until the police arrived – ignorance is bliss!”

jump to conclusions

A person who jumps to conclusions reaches a decision or makes a judgement too fast, before taking the time to check out all the facts.
“We haven’t got the full story yet so let’s not jump to conclusions.”

know better than to do something

If you know better than to do something, you are experienced or wise enough not to do it.
“You should know better than to go sailing in stormy weather.”

know the ropes

Someone who knows the ropes is familiar with the way something is done and/or knows how to do it.
“Charlie can fill in for Sam. He knows the ropes.”

know someone inside out

If you know someone inside out, you know them very well.
“Sue and Anne have been friends since childhood. They know each other inside out.”

know the score

When you know the score, you are well-informed about a situation and know what to expect.
“If Laura damages the car, her dad won’t lend it to her again. She knows the score.”

know your own mind

If you know your own mind, you know what you want or like, and are capable of making a decision.
“I don’t want to influence you. You’re old enough to know your own mind.”

know something like the back of your hand

If you know something like the back of your hand, you are very familiar with it or know it in detail.
“Of course I won’t get lost. I know London like the back of my hand!”

(not) know what hit you

If you don’t know what hit you, you are so surprised, shocked or confused by something that you do not know how to react.
“When I was told that I was the winner of the competition, I didn’t know what hit me!”

know which side your bread is buttered

If you know which side your bread is buttered, you know where your interests lie or what will be to your advantage.
“Paul never argues with his father-in-law. He knows which side his bread is buttered.”

learning curve

The length of time needed to learn something new is called the learning curve.
“The new system has a long learning curve so we’ll have to give the staff time to get used to it.”

light bulb moment

A light bulb moment is when you have a sudden moment of inspiration, comprehension or realization.
“Harry had a light-bulb moment when he finally understood what was blocking the mechanism.”

see (something) in a new light

If you see something in a new light, you view it in a way that makes you change the opinion you had before.
“After listening to my colleague, I began to see things in a new light.”

lose the plot

If a situation becomes so confusing that you are unable to understand what is happening or what you are supposed to do, you lose the plot.
“His instructions were so long and confusing that I just lost the plot!”

lose the thread

If you lose the thread of a conversation or story, you are unable to follow it.
“There were so many interruptions during the film that I completely lost the thread.”

(a) lost ball in high weeds

Someone who is totally confused, and doesn’t know what they are doing or how to do it, is a lost ball in high weeds.
“The new intern in a lost ball in high weeds – he has no idea now to begin the task he’s been given.”

make sense of something

If you make sense of something, you understand it or find the meaning.
“I couldn’t make sense of the instructions.”

miss the point

If you miss the point you fail to understand the essential part of what has been said.
“Sam missed the point. It’s not the job that’s the problem, it’s the amount of work it involves for one person.”

not/never miss a trick

If a person never misses a trick, they are very alert and aware of everything that is happening around them.
“The old lady next door will know if Bill is there or not – she never misses a trick!”

not playing with a full deck

Someone who is not playing with a full deck (of cards) lacks intelligence or does not have full mental abilities.
“Old Mrs.Whitehead was not playing with a full deck when she bought that fancy lawnmower!”

not the brightest bulb in the box
not the sharpest knife in the drawer
not the sharpest tool in the shed

‘Sharp’ and ‘bright’ both mean ‘clever’ or ‘intelligent’.
These are a few of the expressions used to say that someone is not very intelligent. There are many others.
“Max has failed the exam for the third time! He’s obviously not the brightest bulb in the box!”
“Nobody was surprised when Johnny misunderstood the message. We all know he’s not the sharpest knife in the drawer!”

muddy the waters

If you muddy the waters, you make something less clear by giving confusing information.
“I had difficulty understanding, and Alan’s explanation just muddied the waters!”

(a) no-brainer

A decision or choice that requires little or no thought, because the best option is so obvious, is called a no-brainer.
“The choice was between a cash refund or having the amount credited to my account – it was a no-brainer. I took the cash!”

out of your depth

If you are out of your depth, you are unable to understand a subject or deal with a situation because it is too difficult for you.
“The level of the class was too high for me, so very quickly I felt out of my depth.”

out to lunch

To say that someone is out to lunch means that they seem to be either unaware of what’s going on around them, or unable to understand what is happening.
“He’s hopeless as a leader – considererd as ‘out to lunch‘ by the group.”

the penny drops

When a person has difficulty understanding or realizing something, and then the penny drops, they finally understand.
“The teasing continued for some time until the penny dropped and the boy realized it was a joke!”

put two and two together

A person who can is capable of reaching the right conclusion based on the information they have.
“Forget your explanation. She won’t believe you. She can put two and two together!”

quick off the mark

If someone is quick off the mark, they are quick to react to an event or take advantage of an opportunity.
“You’ve got to be quick off the mark when stores announce special offers.”

quick/slow on the uptake

Someone who is quick or slow on the uptake is quick or slow to understand what is meant.
“Please explain the problem in simple words – I’m a bit slow on the uptake!”

rocket science

If you say ‘it’s not rocket science’ or ‘no need to be a rocket scientist’, you are emphasizing that something presents no major difficulty.
“Bob will explain how it works. Don’t worry – it’s not rocket science!”

(a) sharp cookie

Someone who is not easily fooled or deceived is a sharp cookie.
“You can’t fool my grandmother. She’s a sharp cookie!”

(as) sharp as a tack

A person who is as sharp as a tack is able to think quickly and learn very fast.
“You won’t have to explain it to him twice. He’s as sharp as a tack

shed light

If you shed light on something, you help to explain it or make it easier to understand.
“It was hoped that the testimony of the witnesses would shed light on the causes of the accident.”

(a) smart alec

A smart alec is an annoying self-assertive person who tries to show off how clever they are.
“Some smart alec interrupted the game claiming that the answers were incorrect!”

street smart/street wise

A person who is street-smart or streetwise has enough experience and knowledge about life in the city to be able to deal with difficult or dangerous situations.
“The kids living in this area are all street-smart – they’re in less danger than us.”

strike home

When somebody’s comments or remarks strike home, they make you fully understand the situation.
“The seriousness of his injuries struck home as he listened to the surgeon.”

suss out

If you suss out something, such as a problem or a situation, you examine it and manage to understand it.
“Ask Jack to explain – he’s got it all sussed out!”

tech savvy

People who are tech savvy have sufficient technical knowledge and skills to be comfortable using computers and other electronic devices.
“Many students are more tech-savvy than their teachers.”

there is one born every minute

This expression means that there are many people in the world who are stupid or easily fooled.
“He really believed the boy found the money on the street? There’s one born every minute!”

tie yourself up in knots

If you tie yourself up in knots, you become totally confused or confuse others when trying to explain something.
“Sandy tied herself up in knots trying to explain the rules of the game.”

tunnel vision

If a person has tunnel vision, they focus on only one aspect of something, or they are unable to see more than one way of doing things.
“Our manager has tunnel vision. He sees no reason to change anything.”

use one’s noodle

If you use your noodle, you use your brain or your common sense.
“How did I figure that out? I just used my noodle!”

(a) walking encyclopaedia

This term refers to a person who is very knowledgeable about a lot of subjects.
“The origin of Halloween? Ask Jill – she’s a walking encyclopaedia!”

weigh your words

If you weigh your words, you choose your words carefully in order to express exactly what you mean and avoid any misunderstanding.
“At the press conference he spoke very clearly, weighing his words.”

get wires crossed

If people get their wires crossed, they misunderstand each other or are confused about what was said.
“We must have got our wires crossed. I thought we were to meet at the hotel.”

wise after the event

When, after something has happened, someone realises what could have been done to prevent it from happening, they are wise after the event.
“I should have realised the boy was in difficulty and offered to help, but it’s easy to be wise after the event.”

wise for their years / wise beyond their years

Someone who is wise for their years or wise beyond their years has more knowledge and experience that most people at their age.
“She’s still a child but she’s wise beyond her years.”

wise up / get wise (to something)

If you wise up or get wise to something, you become fully aware of the facts and are no longer fooled.
“When Mike finally wised up to the methods being used, he resigned from the company.”

none the wiser

If you do not know more about something after hearing or reading an explanation, or if you fail to find information on the subject, you are none the wiser.
“I tried to understand the voting system but I was none the wiser after reading the explanation.”

wrap your brain around (something)

If you concentrate on something in an effort to understand, you wrap your brain around it.
“I need a translation of this report urgently, so wrap your brain around it fast!”