The aim of this study is to suggest the core-functions and restrictions of the connective ending ``-neunde`` for Korean language education. This study was stated as follows. Firstly, the content about the main semantic-functional of ``-neunde`` in Korean grammar books and text books was analysed. According to the results, grammar description and examples provided in Korean grammar books and texk books about ``-neunde`` are not sufficient for understanding the semantic-function of ``-neunde``. Secondly, the core-function of ``-neunde`` were found to be ``establishing background`` and ``detailed explanation`` according to previous studies. In addition, the restrictions while using ``-neunde`` when in establishing background were stated as follows. 1) Mostly, the following clause should be situations that are not expected. 2) The preceding clause is the ancillary information which stated the background. The following clause is the main information which stated the object. It is restricted that the range of background should be bigger than the range of object. If the range of object is close to the background, the preceding clause will take the main function. At this time, instead of using ``-neunde``, connnectives that can take the main function of the preceding clause should be used. 3) The degree of relation between background and object has restriction, too. When the relation degree between background and object is too high or too low, the sentence is prone to be awkward.