Russian is the most geographically widespread language of Eurasia and the most widely spoken of the Slavic languages. Russian belongs to the family of Indo-European languages and is one of three (or, according to some authorities, four) living members of the East Slavic languages, the others being Belarusian and Ukrainian (and possibly Rusyn, often considered a dialect of Ukrainian).
Written examples of Old East Slavonic are attested from the 10th century onwards, and while Russian preserves much of East Slavonic grammar and a Common Slavonic word base, modern Russian exhibits a large stock of borrowed international vocabulary for politics, science, and technology. Due to the status of the Soviet Union as a superpower, Russian had great political importance in the 20th century, and is still one of the official languages of the United Nations.
Russian has palatal secondary articulation of consonants, the so-called soft and hard sounds. This distinction is found in almost all consonant phonemes and is one of the most distinguishing features of the language. Another important aspect is the reduction, or drawling, of unstressed vowels, not entirely unlike a similar process present in most forms of English. Stress in Russian is generally quite unpredictable and can be placed on almost any syllable, one of the most difficult aspects for foreign language learners.
Russian is a Slavic language in the Indo-European family. From the point of view of the spoken language, its closest relatives are Ukrainian and Belarusian, the other two national languages in the East Slavic group. Some academics also consider Rusyn an East Slavic language; others consider Rusyn just a dialect of Ukrainian.
The basic vocabulary, principles of word formation, and, to some extent, inflections and literary style of Russian have been also influenced by Church Slavonic, a developed and partly adopted form of the South Slavic Old Church Slavonic language used by the Russian Orthodox Church. Upon annexion of the Novgorod by Muscovy in 1478, Old-Novgorod dialect although vanished during 15–16 century, played a significant role in formation of the modern Russian language. The literary Russian has also a noticeable similarity with the modern Bulgarian language sharing about 60% vocabulary in fiction literature and up to 80% of the words used in journalistic genre while having notable differences in grammar.
However, the East Slavic forms have tended to remain 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 slightly different meanings. For details, see Russian phonology and History of the Russian language.
Russian phonology and syntax (especially in northern dialects) have also been influenced to some extent by the numerous Finnic languages of the Finno-Ugric subfamily: Merya, Moksha, Muromian, the language of the Meshchera, Veps etc. These languages, some of them now extinct, used to be spoken right in the center and in the north of what is now the European part of Russia. They came in contact with Eastern Slavic as far back as the early Middle Ages and eventually served as substratum for the modern Russian language. The Russian dialects spoken north, north-east and north-west of Moscow have a considerable number of words of Finno-Ugric origin. The vocabulary and literary style of Russian have also been greatly influenced by Greek, Latin, French, German, and English. Modern Russian also has a considerable number of words adopted from Bulgarian, Tatar and some other Turkic languages.
According to the Defense Language Institute in Monterey, California, Russian is classified as a level III language in terms of learning difficulty for native English speakers,  requiring approximately 780 hours of immersion instruction to achieve intermediate fluency. It is also regarded by the United States Intelligence Community as a "hard target" language, due to both its difficulty to master for English speakers as well as due to its critical role in American foreign policy.
Russian is primarily spoken in Russia and, to a lesser extent, the other countries that were once constituent republics of the USSR. Until 1917, it was the sole official language of the Russian Empire. During the Soviet period, the policy toward the languages of the various other ethnic groups fluctuated in practice. Though each of the constituent republics had its own official language, the unifying role and superior status was reserved for Russian. Following the break-up of 1991, several of the newly independent states have encouraged their native languages, which has partly reversed the privileged status of Russian, though its role as the language of post-Soviet national intercourse throughout the region has continued.
In Latvia, notably, its official recognition and legality in the classroom have been a topic of considerable debate in a country where more than one-third of the population is Russian-speaking, consisting mostly of post-World War II immigrants from Russia and other parts of the former USSR (Belarus, Ukraine). Similarly, in Estonia, the Soviet-era immigrants and their Russian-speaking descendants constitute about one quarter of the country's current population.
A much smaller Russian-speaking minority in Lithuania has largely been assimilated during the decade of independence and currently represent less than 1/10 of the country's overall population. Nevertheless, around 80% of the population of the Baltic states are able to hold a conversation in Russian and almost all have at least some familiarity with the most basic spoken and written phrases. The Russian occupation of Finland in 1809–1918, however, has left few Russian speakers to Finland. There are 33, 400 Russian speakers in Finland, amounting to 0.6% of the population. 5000 (0.1%) of them are late 19th century and 20th century immigrants, and the rest are recent immigrants, who have arrived in the 90's and later.
In the twentieth century, Russian was widely taught in the schools of the members of the old Warsaw Pact and in other countries that used to be satellites of the USSR. In particular, these countries include Poland, Bulgaria, the Czech Republic, Slovakia, Hungary, Romania, and Albania. However, younger generations are usually not fluent in it, because Russian is no longer mandatory in the school system. It was, and to a lesser extent still is, widely taught in Asian countries such as Laos, Vietnam, and Mongolia due to Soviet influence. Russian is still used as a lingua franca in Afghanistan by a few tribes. It was also taught as the mandatory foreign language requisite in the People's Republic of China before the Sino-Soviet Split.
Russian is also spoken in Israel by at least 750, 000 ethnic Jewish immigrants from the former Soviet Union (1999 census). The Israeli press and websites regularly publish material in Russian.
Sizable Russian-speaking communities also exist in North America, especially in large urban centers of the U.S. and Canada such as New York City, Philadelphia, Boston, Los Angeles, San Francisco, Seattle, Toronto, Baltimore, Miami, Chicago, and the Cleveland suburb of Richmond Heights. In the former two Russian-speaking groups total over half a million. In a number of locations they issue their own newspapers, and live in their self-sufficient neighborhoods (especially the generation of immigrants who started arriving in the early sixties). It is important to note, however, that only about a quarter of them are ethnic Russians. Before the dissolution of the Soviet Union, the overwhelming majority of Russophones in North America were Russian-speaking Jews. Afterwards the influx from the countries of the former Soviet Union changed the statistics somewhat. According to the United States 2000 Census, Russian is the primary language spoken in the homes of over 700, 000 individuals living in the United States.
Significant Russian-speaking groups also exist in Western Europe. These have been fed by several waves of immigrants since the beginning of the twentieth century, each with its own flavor of language. Germany, the United Kingdom, Spain, France, Italy, Belgium, Greece, Brazil and Turkey have significant Russian-speaking communities totaling 3 million people.
Two thirds of them are actually Russian-speaking descendants of Germans, Greeks, Jews, Armenians, or Ukrainians who either repatriated after the USSR collapsed or are just looking for temporary employment.
Earlier, the descendants of the Russian emigres tended to lose the tongue of their ancestors by the third generation. Now, because the border is more open, Russian is likely to survive longer, especially because many of the emigrants visit their homelands at least once a year and also have access to Russian websites and TV channels.
Russian is the official language of Russia, and an official language of Belarus, Kazakhstan, Kyrgyzstan and the unrecognized Transnistria, South Ossetia and Abkhazia. It is one of the six official languages of the United Nations. Education in Russian is still a popular choice for many of the both native and RSL (Russian as a second language) speakers in Russia and many of the former Soviet republics.
97% of the public school students of Russia, 75% in Belarus, 41% in Kazakhstan, 25% in Ukraine, 23% in Kyrgyzstan, 21% in Moldova, 7% in Azerbaijan, 5% in Georgia and 2% in Armenia and Tajikistan receive their education only or mostly in Russian, although the corresponding percentage of ethnic Russians is 78% in Russia, 10% in Belarus, 26% in Kazakhstan, 17% in Ukraine, 9% in Kyrgyzstan, 6% in Moldova, 2% in Azerbaijan, 1.5% in Georgia and less than 1% in both Armenia and Tajikistan.
Russian-language schooling is also available in Latvia, Estonia and Lithuania, despite the government attempts to reduce the number of subjects taught in Russian.
Russian has co-official status alongside Romanian in seven Romanian communes in Tulcea and Constanta counties. In these localities, Russian-speaking Lipovans, who are a recognized ethnic minority, make up more than 20% of the population. Thus, according to Romania's minority rights law, education, signage and access to public administration and the justice system are provided in Russian, alongside Romanian.