Belarusian (//; беларуская мова belaruskaja mova ) is an official language of Belarus, along with Russian, and is spoken abroad, mainly in Ukraine and Russia. Before Belarus gained independence from the Soviet Union in 1991, the language was only known in English as Byelorussian or Belorussian, transliterating the Russian name, белорусский язык (Belorusskiy yazyk), or alternatively as White Ruthenian (//) or White Russian. Following independence, it has acquired the additional name Belarusian.
Belarusian is one of the East Slavic languages and shares many grammatical and lexical features with other members of the group. To some extent, Russian, Rusyn, Ukrainian, and Belarusian are mutually intelligible. Its predecessor stage is known as Ruthenian (14th to 17th centuries), in turn descended from Old East Slavic (10th to 13th centuries).
In the first Belarus Census of 1999, the Belarusian language was declared as a "language spoken at home" by about 3,686,000 Belarusian citizens (36.7% of the population). About 6,984,000 (85.6%) of Belarusians declared it their "mother tongue". Other sources, such as Ethnologue, put the figure at approximately 2.5 million active speakers.
According to a study done by the Belarusian government in 2009, 72% of Belarusians speak Russian at home, while Belarusian is actively used by only 11.9% of Belarusians. Approximately 29.4% of Belarusians can write, speak, and read Belarusian, while 52.5% can only read and speak it.
Although closely related to other East Slavic languages, especially Ukrainian, Belarusian phonology is distinct in a number of ways. The phoneme inventory of the modern Belarusian language consists of 45 to 54 phonemes: 6 vowels and 39 to 48 consonants, depending on how they are counted. When the nine geminate consonants are excluded as mere variations, there are 39 consonants, and excluding rare consonants further decreases the count. The number 48 includes all consonant sounds, including variations and rare sounds, which may be semantically distinct in the modern Belarusian language.