成语：chéng yǔ (idiom)
语言词汇中的一部分定型的词组或短句。汉语成语有固定的结构形式和固定的说法，表示一定的意义，在语句中是作为一个整体来应用的，多数为4个字，也有3字的以及4字以上的成语，有的成语甚至是分成两部分，中间有逗号隔开。
【定义】
所谓成语是语言中经过长期使用、锤炼而形成的固定短语。它是比词大而语法功能又相当于词的语言单位。
【形式】
成语一般都是四字格式，也有二字、三字、五字等成语。如“五十步笑百步”、“ 欲速则不达”、“ 醉翁之意不在酒”。成语一般用四个字,这大概是因为四字容易上口。如我国古代的诗歌总集《诗经》，就以四字句为多，古代历史《尚书》，其中四字句也有一些。后来初学读的三、百、千 《三字经》《百家姓》《千字文》，其中后两种即全为四字句。《四言杂字》《龙文鞭影》初、二、三集，都是四言。这虽然是训蒙书，也足以说明四字句之为人所喜爱、所乐诵。古人有些话，本来够得上警句，可以成为成语。只是因为改变为四字，比较麻烦，也就只好把它放弃，作为引导语来用。例如"宋朝范仲淹的《岳阳楼记》，有"先天下之忧而忧，后天下之乐而乐"之语，意思很好，但因字数较多的关系，就没能形成成语，我们只能视为警句，有时引入文章。而如"吃苦在前，享乐在后"，就容易说，容易记，便可以成为成语。而同在《岳阳楼记》中的文句"百废俱兴"，因为是四字，就成了成语。
英文（我是用“有道翻译器”翻译的，但很难理解为什么要英文，有些熟语翻译器可能译不过来的……最好能找个专业人士读一遍看看）
idiom
Part of the vocabulary of phrases or sentences. Chinese idioms have fixed structure form and fixed, the significance, in that statement is used as a whole, the majority of four words, there are also three words and idioms above 4 words, some of the idioms and even is divided into two parts, commas.
[definition.
So-called idiom is used in the language through long-term temper, and fixed phrase. It is larger than the words and grammar function and the language units to word.
The form.
Idioms are generally four word format, also have two words, dirty, five words such idiom. Such as "the pot calling the kettle black" and "more haste, less speed", "continued rejection of the". Idioms usually use four word, it's because of four words flowing easily. As China's ancient of poems, just four words, ancient history, which holds the four words have some. Later, read three beginners, thousands of the embedded BaiGuXing ", "QianZiWen, hind two kinds of all four words for that. The SiYan ZaZi ", "LongWen BianYing", two, three, are SiYan. Although it is put to four books, also words of love and joy recitation. The ancients some words, had enough for one, can become idiom. Just because change for four words, more troublesome, also had to abandon it, as a guide to using language. For example "song of the yueyang tower fan zhongyan," the first and after all, the pleasure of music ", meaning is very good, but because the relationship between words, no more can form the idiom, we can only as a millipede, sometimes into articles such as ". But before pleasure ", it is easy to remember, he said, can become the idiom ". And with the text "of yueyang BaiFeiJuXing", because it is four words, become the idiom.