1.3 Research Design
This paper focuses on the subtitle translation of the emotional expressions between different cultures. Based on the previous study, it will take “functional equivalence”  
as theoretical basis to analyze emotional words in The Big Bang Theory ,combining the study of cultural turn in translation.

The focus of this paper is the study of the influence of popular expressions in network  on subtitling, aiming to realize the successful rendering of cultural implications in translation so as to make contributions to the better exchanges between different cultures.

2. Functional Equivalence Theory
This theory was put forward by American linguist Nida E.A which means that in the process of translation a more natural and equivalent way is used to translate the original text from semantic and stylistic aspects. “ Realistically speaking，functional equivalence is the readers of a translated text should be able to comprehend it to the point that they can conceive of how the original readers of the text must have understood and appreciated it. Ideally speaking,functional equivalence is the readers of a translated text should be able to understand and appreciate it in essentially the same manner as the origingal readers did.”(Shi Qiong, Yan Xin, 2009: 12-14)

2 .1 Principles of Functional Equivalence Theory
Functional equivalence mainly includes four aspects: word equivalence, syntax equivalence, discourse equivalence and style equivalence. Complete equivalence is impossible, so what the translators should do is to close to the perfect situation.

(1)    content the first,form the second
Functional equivalence does not require translate word to word translation. Instead, it asks for the effect of translation to close to the original content. When the content contradicts with the form, translators should not stick to the text structure, but focus  
on the equivalence of content. A good version acquires that the reaction of its readers should be the same of that of the original readers, the former readers can appreciate and understand the version just as the latter read the original text.

(2)    equivalence of the highest level and that of the lowest level
The lowest level of equivalence of a version is that the readers can understand the works just as the original readers know the original works, but to get the same feeling of the original readers, the translators should make some adjustments: First, translators can adopt a way of superscribing to annotate special situations, and this way can meet the readers’ needs for knowledge, unwinding their queries; Second, translators should make adjustments on the level of grammar and culture. Grammatical differences are easy to find out and make changes, but cultural differences are difficult to make up and if not taken carefully, misunderstanding and problems will emerge inevitably. To get the highest level of equivalence, translators should grasp the essence of the original text as a whole, and get a excellent understanding of two differert cultures , then they can shift the cultural concepts easily and accurately.

2.2 Nord’s Functionalist Approach to Translation
German scholors Christiane Nord is one leader in the field of translation study. She put forward the “function plus loyalty” theory basing on the previous researches in 1990s. There are three main factors about her theory: First, the purpose of translation ranks above all fixed factors. She thought that the client who require the translation of a work dominates the whole situation, so what a translator should do is to subordinate to his/her requirements; Second, translation should follows the original text faithfully , free rewriting is not in the category of translation. Nord indicated that “Loyalty” refers to the interpersonal relationship, it is different from faithfulness which just   从《生活大爆炸》看美剧字幕翻译的文化转向(3):http://www.youerw.com/yingyu/lunwen_2419.html