In 1986, Nida put forward the conception of functional equivalence. He explained that there are no essential distinctions between functional equivalence and dynamic equivalence. In his point of view, dynamic equivalence is meant to stress the superiority of content equivalence comparing with form equivalence. People would misperceive that there is contradiction between content and form. To highlight the communicative function and avoid the misunderstanding, Nida firstly put forward functional equivalence theory. He pointed out that “Basically, dynamic equivalence has been described in terms of functional equivalence．The translation has been defined on the basis that the receptors of a translation should comprehend the translated text to such all extent that they call understand how the original receptors must have understood the original text.” (Nida, E.A. 1993: 30) In his book, Language, Culture and Translating, Nida claimed different degrees of adequacy from minimal to maximal effectiveness on the basis of both cognitive and experiential factors. The Minimal definition is “The readers of a translated text should be able to comprehend it to the point that they call conceive of how the original readers of the text must have understood and appreciated it.” And the Maximal definition is “The readers of a translated text should be able to understand and appreciate it in essentially the same manner as the original readers did.” (Nida, E.A. 1993: 118)

2.2 The Definition, Classification and Features of Subtitle

Subtitles are the simple and precise words which occur at the bottom of the screen. It is used to help audience to better understand the play. Subtitle translation is a visual track of target language subtitles added to the source language sound track, repeating the instant dialogue in the form of text. In order to convey audience the precise message, the subtitle need to be defined and the primary theory to guide the subtitle translation practice need to be found out. Although the ultimate goal of subtitle translation is to serve the audiences, there are different standards to judge the different kinds of text. For example, when translating science and technology text, the translator must be careful in the use of words. While for the literature works the translator had better apply some rhetoric devices.