Nivkh or Gilyak (ethnonym: нивхгу, Japanese: ニヴフ語/ギリヤーク語 nivufu-go/giriyāku-go)) is a language spoken in Outer Manchuria, in the basin of the Amgun (a tributary of the Amur), along the lower reaches of the Amur itself, and on the northern half of Sakhalin. 'Gilyak' is the Manchu appellation. Its speakers are known as the Nivkhs.
Nivkh is a language isolate; i.e., it does not appear to be related to any other language. For classification convenience, it is included in the group of Paleosiberian languages. Many words in the Nivkh language bear a certain resemblance to words of similar meaning in other Paleosiberian languages, Ainu, Korean, or Altaic languages, but no regular sound changes have been discovered to systematically account for the vocabularies of these various languages, so any lexical similarities are considered to be due to chance or to borrowing. Recently, the Nivkh language was included in the controversial Eurasiatic languages hypothesis by Joseph Greenberg. Nivkh is divided into four dialects, the Amur dialect, the North Sakhalin dialect, the South Sakhalin dialect, and the East Sakhalin dialect.
The lexical and phonological differences between the dialect spoken by the Nivkhs of the Amur River basin and the dialect spoken by the Nivkhs of Sakhalin Island are so great that some linguists have classified them as two distinct languages belonging to a small Nivkh language family. Other linguists have emphasized the high degree of variability of usage among all Nivkhs; even within the Amur or Sakhalin dialect zone, there is said to be great diversity depending on the village, clan, or even individual speaker.
The grammar of Nivkh is highly synthetic, with a developed case system, as well as other grammatical markers, but no grammatical 'gender'. Nivkh is unique for the high degree of incorporation between words. For example, those morphemes which express spatial relationships (prepositions or postpositions in many other languages) are incorporated into the noun to which they relate. A single word may consist of a combination of several roots, nouns, verbs, and affixes in order to express a particular meaning. Thus, in Nivkh, the formation of each individual word is significant to the sentence.
The population of ethnic Nivkhs has been reasonably stable over the past century, with 4,549 Nivkhs counted in 1897, and 4,673 in 1989. However, the number of native speakers of the Nivkh language among these has dropped from 100% to 23.3% in the same period, so that there are now just over 1,000 first-language speakers left.
The mid front vowel expected in a five-vowel system may have in the past developed into a close-to-mid front unrounded diphthong, represented in Maddieson's description of the language as /ɪe/.