Kiswahili is spoken by an estimated 80 million people in East and Central Africa. It is the official language in Tanzania and Kenya, and is also used in Uganda, Somalia, Mozambique, Malawi, Rwanda, Burundi, Zambia, and Congo (formerly Zaire). The vast majority of speakers of Kiswahili are native speakers of other African languages and use Kiswahili as a lingua franca. After Arabic, Kiswahili is the most widely understood language in Africa. History is the study of change over time, and it covers all aspects of human society. Political, social, economic, scientific, technological, medical, cultural, intellectual, religious and military developments are all part of history.