idioms

by heart (from memory, memorized) We had to learn the entire poem by heart. I have dialed your number so many times that I know it by heart.   by heart – English Vocabulary

break someone’s heart (make someone feel very sad) Jacob broke Sophia’s heart when he left her for another woman. It breaks my heart to think of how they left the animals to starve to death.   break someone’s heart – English Vocabulary

a fly on the wall (an unnoticed observer or listener) I wish I could be a fly on the wall during the negotiations. You should be a fly on the wall to hear what he is saying about you.   fly on the wall – English Vocabulary

a dead duck  informal (an unsuccessful or useless thing, a failure) The project was a dead duck right from the start. (a person who is in great trouble) If Dad finds out what you did, you’ll be a dead duck.   dead duck – English Vocabulary

a cold fish (an unfriendly and unfeeling person) He rarely talks to the others. He’s a cold fish. He never helps his mother clean the house; he is a cold fish.   cold fish – English Vocabulary