The main purpose of this study is to investigate the discourse functions of key in the Jeju language in general. More specifically, this study tries to provide an integral explanation on the seemingly syntactically-governed use of key from a discourse-functional perspective. Traditionally, key has been treated in two ways: sentence ending and emphatic particle. There, however, are no efforts made to provide some unified explanation to the physically separate use of key. Reflecting on traditional understanding, this study assumes that the use of key is pragmatically-controlled phenomenon in nature, suggesting that key has the core meaning around which derivational or secondary meaning are interpretively attached in a given discourse context. The core meaning of key has something to do with the strategy of face-saving. Based on this core meaning, the various secondary meanings could be derived to properly get through the participants`` intentions such as agreement, hold the floor, and sympathetic attitude.