Coherence rule requires the translation must conform to intratextual coherence standard, namely the translation should be of readability and acceptability, and also can make the receiver understand and have significance in the target culture and the communicative context。 The fidelity rule refers to the existence of inter lingual coherence between the original text and the translated text。 This is equivalent to be faithful to the original text in other translation theories, but the degree and form of faithfulness to the original text depend on the purpose of the translation and the translator's understanding of the original text。

Fidelity rule was proposed by Nord。 She found that Skopos theory has two drawbacks: first, because of the differences of cultural patterns, people with different cultural backgrounds have different views on good translation; in addition, if the skopos rule required by the communicative purpose of the translation is opposite to author of original text, then we will abide by the skopos rule rather than fidelity rule。 Therefore, Nord put forward the fidelity rule to solve the cultural differences and the relationship between the participants in translation。 Nord believes that the translator has a moral responsibility to the receiver of the translation and must explain to them what they have done and why。 This is one aspect of fidelity。 On the other hand, it requires the translator to be faithful to the original author。 The translator should respect the original author and coordinate the target text and the author's intention。 Therefore, fidelity rule is mainly concerned with the relationship between the translator and the original author, the customer, the target audience, etc。。 Nord put forward that the translator should follow the guiding principle of "function plus fidelity"。 (Nord 27) 

Briefly speaking, Skopos Theory comprises the idea that translating and interpreting should primarily take into account the function of both the source and target text。