The Isen dialect is a subgroup of the Amami language, which is endangered. The present study clarified the comprehensive system of the Isen dialect from the viewpoint of descriptive linguistics. Section 2 discussed phonology (segmental phonology and indeces of phonemes, syllable structure, and the system of word accent) of the dialect. Section 3 difined word classes and root classes by using morphosyntactic characteristics. Section 4 discussed internal and external structures of verbal predicate including words with an adjective root. Section 5 discussed morphosyntax of noun and nominal predicate. Section 6 disscussed the demonstratives. Demonstratives in the Isen dialect is a cross-over category. Section 7 discussed syntax (word order, valency-changing operation, and subordinate clause). Section 8 discussed functional categories.