Taiwanese (pe̍h-oē-jī: Tâi-oân-oē or Tâi-gí; traditional Chinese: 臺灣話, 臺語; pinyin: Táiwānhuà, Táiyǔ) is a variant of Amoy Min Nan Chinese spoken by about 70 % of Taiwan's population. The largest ethnic group in Taiwan for which Taiwanese is considered a native language is known as Hoklo or Holo (Hō-ló). The correspondence between language and ethnicity is generally true though not absolute, as some Hoklo speak Taiwanese poorly while some non-Hoklo speak Taiwanese fluently. Pe̍h-oē-jī (POJ) is a popular orthography for this language, and Min Nan in general.
Taiwanese is a variant of Amoy Min Nan. It is often seen as a Chinese dialect within the larger Sinitic language family. On the other hand, it may also be seen as a language in the Sino-Tibetan family. As with most "language/dialect" distinctions, how one describes Taiwanese depends largely on one's political views (see Identification of the varieties of Chinese). In any case, the classification may be represented hierarchically as:Sino-Tibetan ⊃ Chinese ⊃ Min ⊃ Min Nan ⊃ Amoy ≈ Taiwanese
Min is the only branch of Chinese that cannot be directly derived from Middle Chinese. This may account for the difficulty in finding the appropriate Chinese characters for some Min Nan vocabulary. This is maybe also part of the reasons why it is mutually unintelligible with Mandarin or other Chinese dialects.
There is both a colloquial version and a literary version of Taiwanese. Spoken Taiwanese is almost identical to spoken Amoy. Regional variations within Taiwanese may be traced back to Amoy variants spoken in Southern Fujian (Quanzhou and Zhangzhou). Taiwanese also contains loanwords from Japanese and the Formosan languages. Recent work by scholars such as Ekki Lu, Sakai Toru, and Lí Khîn-hoāⁿ (also known as Tavokan Khîn-hoāⁿ or Chin-An Li), based on former research by scholars such as Ông Io̍k-tek, has gone so far as to associate part of the basic vocabulary of the colloquial Taiwanese with the Austronesian and Tai language families; however, such claims are still controversial.
A literary form of Min Nan once flourished in Fujian and was brought to Taiwan by early emigrants. Nāi-kèng-kì, the manuscript for a series of plays published during the Ming Dynasty in 1566, is one of the earlist known works. This form of the language is now largely extinct.
Source - Wikipeadia.com