Ukrainian language (ukrayins’ka mova) is the official language of Ukraine. It is one of the East Slavic languages like Russian and Belorussian. These languages use the Cyrillic alphabeth. The language shares some vocabulary with the languages of the neighboring Slavic nations, most notably with Polish, Slovak, Serbian and Russian.
The Ukrainian language traces its origins to the Old Slavic language of early medieval state of Kievan Rus'. Ukrainian language has persisted despite several periods of bans and/or discouragement throughout centuries as it has always maintained a sufficient base among the people of Ukraine, its folklore songs, great musicians, and prominent authors.
During the seven-decade-long Soviet era, the Ukrainian language held the formal position of the principal local language in the Ukrainian SSR. However, practice was often a different story: Ukrainian always had to compete with Russian, and the attitudes of the Soviet leadership towards Ukrainian varied from encouragement
and tolerance to discouragement and, at times, suppression. Russian was in a privileged position in the USSR. Often the Ukrainian language was frowned upon or quietly discouraged, which led to the gradual decline in its usage. Partly due to this suppression, in many parts of Ukraine, notably most urban areas of the east and south, Russian remains more widely spoken than Ukrainian.
Since 1991, independent Ukraine has made Ukrainian the only official state language and implemented government policies to broaden the use of Ukrainian. The government has also mandated a progressively increased role for Ukrainian in the education, media and commerce.
Ukrainian language is currently emerging from a long period of decline. But it is mostly prevalent in Western Ukraine (where it undergone some Polish influence).
In Kiev (Kyiv), both languages Ukrainian and Russian are spoken. Actually, this is a notable shift from the recent past when the city was primarily Russian speaking. The shift is caused, largely, by an influx of migrants from the western regions of Ukraine but also by some Kievans' turning to use the language they speak at home more widely in everyday matters. In northern and central Ukraine, Russian is the language of the urban population, while in rural areas Ukrainian or a mix of Ukrainian and Russian (called "surzhik") is much more common.
This is also true of much of the south and the east. But you can hardly find anybody speaking Ukrainian in Crimea.
Surzhik is a mixture of Ukrainian and Russian languages in which commonly Russian vocabulary is combined with Ukrainian grammar and pronunciation. The vocabulary usage of either of the languages varies greatly with location, or sometimes even from person to person, depending on the level of education, personal experiences, rural or urban residence, origin of interlocutors etc. Surzhyk is often used for comical effect in arts.