Even after the secession of South Sudan in 2011, the Sudan of today is very diverse, with five hundred plus ethnic groups spread across the country's territory, which makes it the third largest country in Africa. The cultures of its ethnic and social groups have been marked by the complex cultural legacy, going back to the spread of Islam, the regional history of the slave trade and by indigenous African cultural heritage. Though some of the ethnic groups still maintain their own African language, most Sudanese today use the distinct Sudanese version of Arabic.