After a comparative investigation of the use of"reserved expressions"in the academic papers on language study and education published in Japan and China,it is found that Japanese papers used far more"reserved expressions"than Chinese papers.

Approach to construct rough fuzzy set based on representation theorem;

The representation theorems of L-fuzzy sets and their applications;

A short proof for the representation theorem of strong negations is presented.

After its expression theorem was given, its operation and operation law were inquired into based on extension principle.

The decomposition theorem and expression theorem with the form of intersection of fuzzy￣ mapping are established, and then the forms of the extension of fuzzy mapping are discussed,and a series of important results is obtained.

To facilitate Japanese teaching for Japanese leamers in China, the author explores the teaching of Japanese negation expression in this paper.