In Japanese language, like other language i presume, there is also a varieties of way to speech. Or in another words is dialects and social style of speech. There are a large number of dialects throughout the four main islands and the smaller islands of Okinawa and others."Through painstaking research, we now have conclusive evidence for the genetic relationships of the major languages of the world. English, along with a host of languages spoken in Europe, Russia, and India, belong to the Indo-European family of languages. In contrast, there is no conclusive evidence relating Japanese to a single family of languages. The most prominent hypothesis places Japanese in the Altaic family, which includes Turkish, Tungusic, Mongolian, and Korean, with the closest relationship to Korean. According to Roy Andrew Miller, the original Altaic language was spoken in the Transcaspian steppe country, and the speakers of this language undertook massive migrations before 2,000 B.C., spreading this language family from Turkey in the west to Japan in the east. However, this hypothesis is inconsistent with some major features of Japanese, leading some scholars to turn to the languages of the South Pacific in the Austronesian family for clues of genetic relationship. A hypothesis that has currency among a number of Japanese historical linguists is a "hybrid" theory that accepts the relationship to the Altaic family, but also hypothesizes influence from Austronesian languages possibly through heavy lexical borrowing. It is also important to note that in the northern island of Hokkaido, the Ainu people, who are physically and culturally different from the rest of the Japanese, speak a language that has even more successfully escaped attempts to relate it to a single language family.
With the introduction of the writing system from China starting about 1,500 years ago, the Japanese people began to extensively record their language through poetry and prose. The language of that era, called Old Japanese, had a number of features that have been lost through time. For example, Susumu Ono has argues that Old Japanese had eight vowels instead of the five that we see today. There were also a number of grammatical and morphological features that no longer exist. The transition from Old Japanese to Modern Japanese took place from about the twelfth century, A.D., to the sixteenth century, A.D."
Some dialects such as those spoken in the southern parts of Japan (Kyushu, Okinawa) are virtually incomprehensible to the speakers of other dialects, requiring the use of the standard (or "common") dialect for communication.
The two dialect families with the largest number of speakers are the dialect spoken in and around Tokyo, which is equivalent to the "common" dialect, and the dialects of the Kansai region spoken in western Japan in cities such as Kyoto, Osaka, and Kobe. Due to the spread of the common dialect through television and radio, most people outside the Tokyo region speak the common dialect as well as the dialect of their area.
For example I give here is from the western Japan (関西弁)
>> I don't understand
Standart Japanese Language is 分かりません (wakarimasen) but in western Japan 分からへんや(wakarahenya) something like that. ^^