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