Russian belongs to the family of Indo-European languages and is one of the four living members of the East Slavic languages (which in turn is part of the larger Balto-Slavic branch). Written examples of Old East Slavonic are attested from the 10th century onward.
It is the most geographically widespread language of Eurasia and the most widely spoken of the Slavic languages (followed by Polish and then Ukrainian). It is also the largest native language in Europe, with 144 million native speakers in Russia, Ukraine and Belarus. Russian is the eighth most spoken language in the world by number of native speakers and the seventh by total number of speakers. The language is one of the six official languages of the United Nations. Russian is also the second most widespread language on the Internet after English.
Russian distinguishes between consonant phonemes with palatal secondary articulation and those without, the so-called soft and hard sounds. Almost every consonant has a hard or a soft counterpart, and the distinction is a prominent feature of the language. Another important aspect is the reduction of unstressed vowels. Stress, which is unpredictable, is not normally indicated orthographically though an optional acute accent (знак ударения, znak udareniya) may be used to mark stress, such as to distinguish between homographic words, for example замо́к (zamók, meaning a lock) and за́мок (zámok, meaning a castle), or to indicate the proper pronunciation of uncommon words or names.
Russian is an East Slavic language of the wider Indo-European family. It is a lineal descendant of the language used in Kievan Rus', a loose conglomerate of East Slavic tribes from the late 9th to the mid 13th centuries. From the point of view of spoken language, its closest relatives are Ukrainian, Belarusian, and Rusyn, the other three languages in the East Slavic languages. In many places in eastern and southern Ukraine and throughout Belarus, these languages are spoken interchangeably, and in certain areas traditional bilingualism resulted in language mixtures such as Surzhyk in eastern Ukraine and Trasianka in Belarus. An East Slavic Old Novgorod dialect, although vanished during the 15th or 16th century, is sometimes considered to have played a significant role in the formation of modern Russian. Also Russian has notable lexical similarities with Bulgarian due to a common Church Slavonic influence on both languages, as well as because of later interaction in the 19th and 20th centuries, although Bulgarian grammar differs markedly from Russian. In the 19th century, the language was often called "Great Russian" to distinguish it from Belarusian, then called "White Russian" and Ukrainian, then called "Little Russian".
The vocabulary (mainly abstract and literary words), principles of word formations, and, to some extent, inflections and literary style of Russian have been also influenced by Church Slavonic, a developed and partly russified form of the South Slavic Old Church Slavonic language used by the Russian Orthodox Church. However, the East Slavic forms have tended to be used exclusively in the various dialects that are experiencing a rapid decline. In some cases, both the East Slavic and the Church Slavonic forms are in use, with many different meanings. For details, see Russian phonology and History of the Russian language.