idioms

a hard nut to crack (something that is difficult to do or understand) This problem is indeed a hard nut to crack. The fourth question in the exam was a hard nut to crack.   hard nut to crack – English Vocabulary

    a piece of cake (very easy) The driving test was a piece of cake. Climbing this mountain is a piece of cake for an experienced climber.   piece of cake – English Vocabulary

  apple of your eye (someone you like the most) Her youngest daughter was the apple of her eye. Jacob is his only child and the apple of his eye.   apple of your eye – English Vocabulary

    a different kettle of fish (a completely different type of person or thing) My brother is a very different kettle of fish from me. Our new office is a different kettle of fish altogether.     different kettle of fish – English Vocabulary

  brain dead (mentally exhausted and unable to think normally) If you don’t get enough sleep, you’ll be brain-dead in the morning. (very stupid or careless) How can you have a conversation with such a brain-dead person? brain dead – English Vocabulary