Zambia Urban dwellers sometimes differentiate between urban and rural dialects of the same language by prefixing the rural languages with 'deep'. Most will thus speak Bemba and Nyanja in the Copperbelt; Nyanja is dominantly spoken in Lusaka and Eastern Zambia. English is used in official communications and is the language of choice at home among – now common – intertribal families. This continuous evolution of languages has led to Zambian slang which can be heard in daily life throughout Lusaka and other major cities. Portuguese has been introduced into the school curriculum due to the presence of a large Portuguese-speaking Angolan
Swahili language for those areas, and the standard orthography for Swahili was adopted. Swahili has become a second language spoken by tens of millions in three African Great Lakes countries (Tanzania, Kenya, and the DRC) where it is an official or national language. In 2016, Swahili was made a compulsory subject in all Kenyan schools. Swahili and closely related languages are spoken by relatively small numbers of people in Burundi, Comoros, Malawi, Mozambique, Uganda, Zambia and Rwanda. The language was still understood in the southern ports of the Red Sea in the 20th century. Some 80 percent of approximately 49 million Tanzanians