Speak English Naturally: 20 Popular Idioms and How to Use Them

Idioms are the colorful expressions that make a language come alive. They reveal how people think, feel, and even joke — offering a glimpse into everyday English culture.

For language learners, idioms are a powerful way to sound more natural, understand conversations faster, and connect more deeply with native speakers.

Here are 20 popular English idioms, grouped by theme, with explanations and examples to help you use them confidently in your daily life or at work.

Everyday Expressions

1. A piece of cake

Something that is very easy.

“That grammar test was a piece of cake — I finished in 10 minutes!”

2. Once in a blue moon

Something that happens very rarely.

“We only go skiing once in a blue moon.”

3. Break a leg

A way to wish someone good luck — especially before a performance or big presentation.

“You’ll do great in your meeting today — break a leg!”

4. Under the weather

Feeling slightly ill.

“I think I’ll stay home — I’m a bit under the weather.”

5. When pigs fly

Something that will never happen.

“He’ll arrive on time when pigs fly.”

At Work or School

6. On the ball

To be alert, organized, and effective.

“Maria is really on the ball — she always spots mistakes before anyone else.”

7. To cut corners

To do something in a quick or careless way to save time or money.

“We can’t cut corners on this client project — quality comes first.”

8. Steal someone’s thunder

To take credit for someone else’s idea or success.

“He stole my thunder by presenting my idea first.”

9. To kill two birds with one stone

To achieve two goals with one action.

“I studied vocabulary while commuting — killed two birds with one stone.”

10. See eye to eye

To agree completely.

“After some discussion, we finally saw eye to eye on the marketing plan.”

Feelings and Emotions

11. Have butterflies in your stomach

To feel nervous or excited.

“I had butterflies in my stomach before my first speech in English.”

12. A tough cookie

Someone who is strong and determined.

“She’s a tough cookie — she never gives up.”

13. A blessing in disguise

Something that seems bad at first but turns out to be positive.

“Losing that job was a blessing in disguise — it led me to a better opportunity.”

14. I could eat a horse

Used when you’re extremely hungry.

“After the long hike, I could eat a horse.”

15. By the skin of your teeth

When you narrowly avoid failure or danger.

“I passed the exam by the skin of my teeth.”

Conversation and Communication

16. Let the cat out of the bag

To reveal a secret, often by accident.

“He let the cat out of the bag about the surprise party.”

17. Beat around the bush

To avoid talking about the main issue.

“Stop beating around the bush and tell me what you think.”

18. Judge a book by its cover

To make assumptions based on appearance.

“Don’t judge a book by its cover — she’s much more experienced than she looks.”

19. Speak of the devil

Said when the person you’re talking about appears.

“Speak of the devil — we were just mentioning your name!”

20. Cost an arm and a leg

Something that’s very expensive.

“That conference trip cost an arm and a leg, but it was worth it.”

Why Learning Idioms Matters

Idioms add personality, humor, and emotion to everyday English. They make your speech sound more fluent — not just grammatically correct, but alive.

Understanding idioms also helps you interpret jokes, TV shows, or workplace conversations more easily.

Final Thoughts

Learning idioms isn’t about memorizing lists — it’s about understanding how people really communicate.

Start small, use them in context, and soon they’ll become a natural part of your English vocabulary.