An urban district or urban raion (Ukrainian: Райони у містах України) is an administrative division of certain cities in Ukraine. An urban district is subordinate to the city administration
There are 111 districts in 19 cities of Ukraine. The cities that contain district division in a city usually are of national (such as Kiev and Sevastopol) or regional significance. The number of districts in city per region varies between the minimum of two and up to 21 in Donetsk Oblast (the maximum districts in a single city are in Kiev).
More information on the Wikipedia page [1]