By the two types of derivatives,namely,loaning and replacing-extension and the combination-assimilation,qing in qing yun series means the sky.

The paper puts forward four methods to understand the word meaning correctly To understand the word meaning by word matching, context clues, grammatical characteristics and extended meaning.

The paper investigates the development of the extended meanings of the Chinese expression piru(譬如), particularly when it is used as synonymous to dangzuo(当作)or yaoshi(要是).

Transformation in English-Chinese translation——method of extension;

There are two contributions XU Kai has made to the theory of extension of word meaning: First,based on XU Shen s The Six Categories of Chinese Characters and the relationship between borrowed meaning and original meaning,XU Kai categorized the borrowed words,which helped the Qing linguists to further define the concepts of loan and extension,and to straighten out the relationship between the two.

The difference is illustrated in this paper by a large number of examples based on the extension of words meaning,the development of melonymy,etc.

In this paper,an irrational inequality is generalized and extended in many-sided,a class of new irrational inequalities are established,which are interesting and useful.

For instance,some common words which have no medical meaning need to be extended to conform to the ex pression of medical science; the long and complic.

We will find that because Chinese is an isolated languge, compared with Indo-European languges, there are three differences of semantic changes in Chinese: first, semantic extended in Chinese doesn’t limit in some meaning’s domain; second, different type of subjective reasoning can impact semantic change of the same word; and the last, the meanings of Chinese can only increase, but not reduce.