【正文】【Abstract】  For Chinese students， it's a rather tough task to learn English， and English idioms， in particular. It's even harder to understand various figures of speech， among which metaphor is one of the most difficult to master. In general， students who have a remarkable knowledge of English may be not good at grasping metaphor. In traditional terms of rhetorical device， metaphor is a significant rhetorical device. At present， theorists in the field of metaphor believe that metaphor is not merely a linguistic phenomenon， but also a sort of cognitive phenomenon and a way how people think. The relationship between idiom and metaphor is just the same as the relationship between language and thinking. Many researchers have been engaged in researching metaphor both at home and abroad. The research of metaphor can be dated back to L. P. Smith， a British scholar. In 1925， Smith came out a book， which is called Words and Idioms， becoming the representative of the study of idiom. 1960s， linguisticians such as Baser， began to research the deep structure of idiom with the theory of generative transformation， especially idiom's transformational function. The reason why they do not the fixity of idiom is because they thought that fixity is a matter of degree. There exists deficiency in a variety of degrees of transformation. But it still has the potential to transform. Consequently， they put forth degree theory of idiom in fixity. Since 1980s， the study of idiom has stepped into a new stage. Many scholars have begun to get rid of the original research model， breaking many more novel approaches to researching. 
　　【Keywords】 metaphor； English idiom； features； function； application

　　1.Introduction
　　Speaking of English learning， there is always a much momentous and an untoward task in English learning. That is metaphor， which plays an increasingly significant role in English learning， for instance， poems， lyrics， composition， novels， slang， dramas， inaugural speech， idioms and so forth. Metaphor is a type of figures of speech， which enjoys a rather popular application. Owing to its special functions in expression， people of all walks of life tend to use it in their daily communication， public speech， literary works， which will make their language more attractive， powerful， persuasive and full of art respectively. Even in some advertisements， there is an increasing popularity in applying metaphor， which will make its products more attractive and novel. To be frank， it is the powerful function of metaphor that makes it worth applying and studying.
　　Regarding to the structure of this paper， there are six parts all together. In the first part， it presents a concise introduction of the objection， significance and structure of the thesis in the first part. The second part is the literature review， in which the reference materials of this thesis will be generally introduced， also some famous linguisticians acomplishments in metaphor and idiom will also be included. And then the development of idiom will be introduced in the third part. In the fourth part， it will focus on the development of metaphor， and in the fifth part， it will concentrate on the identification of metaphor in idiom with an aim of identifying metaphor and idiom in articles or other reading materials. At last， there comes to a conclusion， in which there will be an overall review of this paper and the possibility of research in the future.
　　2.Literature Review
　　Speaking of the study of metaphor， most researchers have done researches of it from different fields. From the aspect of human features， “the functions and formation of metaphor needs to follow some certain rules， the function of a certain metaphor confines to the concrete context” （Sanford， 2008）. Fernando draws a conclusion that different parts of the body can form an idiom and that the same part of the body can also produce near idioms with different words （Fernando，1996）. Meanwhile， Steen points out that “while probing into the research of metaphor， you will find it difficult to find out the cognitive function of metaphor. The cognitive function of metaphor plays an increasingly important role in literature.” （Steen， 2013）. Researchers， such as Valetta G. Dorset，  Kael， Tina Krennmayr， have done researches of metaphor in terms of its application. 
　　Concerning idiom， there is an increasing number of researches that involves metaphor. The potential expressive capability of metaphor provokes a new trend to study metaphor （Tseng， 2010）.  Some demonstrate that the impact of metaphor on cognitive competence illustrates another aspect of metaphor （Ungerer and Schmid， 1996）. Some illustrate that the formation of fundamental discourse of metaphor is complementary to the formation of metaphor （冯晓虎， 2014）. The research of metaphor in many aspects from the aspect of linguistics explains some abstract questions， which makes it easier to understand metaphor from the aspect of linguistics （胡壮麟， 1998）. When it comes to metaphor， there are various idioms that involved in metaphor. It is not rather uncommon to see that many idioms contain a certain metaphor （King， 2008）. 
　　3.The Development of Idioms
　　Idiom is the essence of language； it reflects the development of society and culture. The development of idiom is affected by many factors.  Firstly， geological situations， British are surrounded by seas in that there are many idioms about voyage and fishing. Moreover， historical and military events influence the development of idioms either. Thirdly， social customs and religious belief.  In terms of idioms， there are many idioms that accompanied with color. Color words that refer to color also contain connotative meaning in culture. Idioms that followed by color words either in Chinese or English convey different information in culture. （周敏，2017）.
　　According to Oxford Advanced Learner’s English-Chinese Dictionary， 
　　“Idiomatic expressions are a special kind of expressional way of language or a kind of arts of human language.”（商务印书馆，2014）.Idioms are termed as the nature of the language， acting as a critical element of the common vocabulary of a language. 
　　Although a majority of scholars both at home and abroad have spent a long time to definite to idiom， it is still quite difficult to give a clear-cut one， for different researchers always lay different stresses on this topic （骆世平， 2006）.
　　4.The Development of Metaphor
　　Roughly， the study of metaphor can be traced back to AD300. That is to say， it begins from Aristotle’s comparison theory， in which he involves something interesting， such as， the definition， types， functions and so on. His illustration about metaphor is called comparison theory. He alleges that metaphor involves in using words that depict one thing refer to the other thing.  Aristotle stated the formation and function of metaphor as a sort of rhetoric device in Poetics and Rhetoric， one of his books.
　　From 1930s to 1970s， scholars began to turn to research metaphor from many aspects such as linguistics， logistics and philosophy. The central subject of the studies that they made is the semantic function of metaphor in language situation. 1930s， after the publication of the book The Philosophy of Rhetoric， interactive theory of metaphor broke a novel way， which transcends the traditional rhetoric that only regards metaphor as a comparison and replacement of words. 
　　5. Identification of Metaphor in Idiom
　　Nominal idioms， which refer to the idioms that take the nouns as the central words.They are idioms nominal in nature and function as nouns in the sentence. This type of English idioms enjoys metaphorical meanings during the process of forming， evolving， applying. Therefore， many metaphors in nominal idioms are closely associated with culture. 
　　For example， “white elephant”， which means “something are expensive but useless”. The idiomatic expression “white elephant” is often used metaphorically to refer to the things that are exorbitant but bootless.  
　　Apparently， what can be predicted from the title is that verbal idioms refer to the idioms that contain verbs that acted as central words in the idiom. They serve as the predicate in the sentence. 
　　6. Conclusion
　　Idiomatic expressions are the essence of the English language， which is large in quantity， all-embracing in content， and extensive in the usage. As is known to all， the English language is really rich in idioms. 
　　Metaphor plays an important role in English idioms， which is an unquestionable fact. In this thesis， it primarily states the history and the development of both idiom and metaphor researches as well as the research of metaphor in the framework of English idiomatic expressions. Moreover， this paper reveals the nature of metaphor by the studying of English idiomatic expressions， with an aim of improving the readers’ understanding ability of metaphor， application ability of English idioms and the cognitive ability to the world by the use of metaphorical thinking as well. However， this thesis only focuses on the study of the usage and identification of metaphor in English idiom. In view of the rapid development of metaphor and idiom， hopefully， there will be more researches both in metaphor and idiom in the future.
　　Bibliography
　　[1]Fernando， C. Idioms and？Idiomaticity [M]. Oxford： Oxford？University， 1996.
　　[2]King， Kevin. 把握英语脉搏——习语中的隐喻[M]. 北京：科学出版社， 2008.
  [3] Oxford Advanced Learner’s English-Chinese Dictionary[M]商务印书馆，2014.
　　[4]段新和. 文化角度下英汉习语的隐喻对比及互译策略研究[J]. 湖北第二师范学院学报， 2009（7）.