Swahili language
The exact number of Swahili speakers, be it native or second-language speakers, is unknown and a matter of debate. Various estimates have been put forward and they vary widely, from 50 million to over 100 million. Swahili serves as a national language of four nations: Tanzania, Kenya, Uganda, and the DRC. Shikomor, the official language in Comoros and also spoken in Mayotte (), is related to Swahili. Swahili is also one of the working languages of the African Union and officially recognised as a lingua franca of the East African Community. South Africa legalized the teaching of Swahili in South African schools as an optional subject beginning in 2020.
Tanzania
Over 100 different languages are spoken in Tanzania, making it the most linguistically diverse country in East Africa. The country does not have a "de jure" official language, although the national language is Swahili. Swahili is used in parliamentary debate, in the lower courts, and as a medium of instruction in primary school. English is used in foreign trade, in diplomacy, in higher courts, and as a medium of instruction in secondary and higher education, although the Tanzanian government is planning to discontinue English as a language of instruction altogether. Approximately 10 percent of Tanzanians speak Swahili as a first language, and up to 90 percent speak it as a second language.