Cursive writing is a way of writing for convenience. "Shuo Wen Jie Zi" says: "There are cursive scripts in Han Xing". The cursive script began in the early Han dynasty, and its characteristics are: keeping the outline of characters, damaging the official rules, rushing away and rushing away quickly. Because of the meaning of grass, it is called cursive script.
Attached picture: Sun's book score
From Baidu Encyclopedia, but I still hope to adopt it.