Idioms are common in both speech and writing. Although you do not have to learn all the idioms in English, you must be familiar with the most common ones.

Straight from the horse’s mouth

When you hear something straight from the horse’s mouth, you hear it from the person actually involved.

John and Mary are getting married. I heard it straight from the horse’s mouth.

Mutton dressed (up) as lamb

Used to describe an older woman who wears clothes that are more suitable for a much younger woman

To pull a rabbit out of the hat

To pull a rabbit out of the hat is to surprise everyone by doing something clever

A wolf in sheep’s clothing

Someone who is dangerous but pretends to be harmless

Beware of him. He is a wolf in sheep’s clothing.

To be a chicken / to be chicken livered

If you are a chicken you are a coward.

Don’t be such a chicken.

To be like a dog with two tails

When you are like a dog with two tails, you are very happy.

Gone to the dogs

When a business goes to the dogs it becomes less successful than it was. When a country goes to the dogs, it becomes less prosperous.

Like a fish out of water

When you are like a fish out of water, you are uncomfortable.

To be a fly on the wall

To want to be somewhere secretly, so that you can overhear what is said

To be as sly as a fox / a sly old fox

To be very clever or cunning

Don’t trust him. He is a sly old fox.

Something is fishy

When something is fishy, it is suspicious.