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