The small group of Hachijō dialects (八丈方言, Hachijō hōgen), natively called Shima Kotoba (島言葉, [ɕima kotoba], "island speech"), depending on classification, either are the most divergent form of Japanese, or comprise a branch of Japonic (alongside mainland Japanese, Northern Ryukyuan, and Southern Ryukyuan).

Based on the criterion of mutual intelligibility, Hachijō may be considered a distinct Japonic language, rather than a dialect of Japanese.

[4] Hachijō is a descendant of Eastern Old Japanese, retaining several unique grammatical and phonetic features recorded in the Azuma-dialect poems of the 8th-century Man'yōshū and the Fudoki of Hitachi Province.

[6] Since at least 2009, the town of Hachijō has supported efforts to educate its younger generations about the language through primary school classes, karuta games, and Hachijō-language theater productions.

Nevertheless, native speakers are estimated to number in the "low hundreds," and younger generations are not learning or using the language at home.

On Hachijō-jima, these are Ōkagō, Mitsune, Nakanogō, Kashitate, and Sueyoshi; on Hachijō-kojima, these were Utsuki and Toriuchi; and the village of Aogashima is its own group.

Finally, there are a small number of words that contain N as a syllable nucleus instead of a vowel, such as NNmakja "tasty" [m̩ː.ma.kʲa] (stem NNma-, cognate to Japanese 美味い uma-i).

[17] In addition to the variations described above, Hachijō also exhibits a handful of other conditioned sound alternations: When followed by the high vowels /u/ or /i/ (short or long), the plosive consonants t /t/ and d /d/ become sibilant affricates, merging into c /t͡s/ and z /d͡z/ respectively, which is also reflected in orthography (as shown here).

Thus, t-j and c-j become cj [t͡ɕ], d-j and z-j become zj [d͡ʑ], s-j becomes sj [ɕ], and n-j becomes nj [ɲ].

Lastly, the coronal affricates c and z have a tendency to be sporadically palatalized to cj and zj; compare Utsuki mizoma [mʲid͡zoma] and Kashitate mizjoma [mʲid͡ʑoma] "sewer, drainage," cognate to Japanese 溝 mizo "ditch.

Non-coalescing vowels are comparatively common in the Utsuki dialect, as [i], [u], and [e] often occur in place of other dialectsʼ ri, ru, and re due to the loss of the phoneme /ɾ/ word-medially.

Compare the following vocabulary:[27] The majority of consonants undergo no special changes when geminated, merely becoming longer, e.g.: t [t] → Qt [tt].

Hachijō is head-final, left-branching, topic-prominent, often omits nouns that can be understood from context, and has default subject–object–verb word order.