Abstract
1. Introduction
2. Linguistic Values
2.1 language and thoughts
2.2 Language Endangerment
2.4 Why worry about ‘language Disappearance’?
2.5 Sustainability
3. Story of Jejueo, the language of Jeju.
3.1 Jeju and Jejueo
3.2 Language and dialect
3.3 Mutually unintelligible
3.4 Jejueo: past to present
3.5 Jejueo in terms of sustainability
4. Conclusion
References