Matching Pairs COMMON IDIOMS IN ENGLISHOnline version A short list of common idioms in English. by kepa olaizola garcia 1 Break a leg. 2 You can´t judge a book by its cover. 3 Let the cat out of the bag. 4 When pigs fly. 5 Sleep on it. 6 Hit the books. 7 Take it easy. 8 Piece of cake. 9 Hit the nail on the head. 10 Costs an arm and a leg. To disclose a secret that was supposed to be kept. Something will never happen. Relax Something that is precisely right. Something is very easy. To think. Good luck. Something is very expensive. To study. You shouldn´t decide upon something based just on outward appearances.