Is exhortation an idiom?

Yes According to the relevant information of idioms, it is inferred that the idiom "Zhang Tian Xia" comes from the biography of Deng Kou in the later Han Dynasty. Idiom is a major feature of traditional culture in China, which has a fixed structure and a fixed sentence, indicating a certain meaning. It is applied to a sentence as a whole, with subject, object, attribute and other components.