Some texts, such as poems, seem untranslatable but must be translated, while some other texts, such as advertisement copies, may seem translatable but mustn't be translated. The judgment of translatability or untranslatability is usually formed on how hard SL texts can be translated into TL texts, but whether and how a translation should be conducted is determined by social requirements, which vary from genre to genre and demand different translation principles and methods for different text types.