Official language to the government in their native languages. In countries that do not formally designate an official language, a "de facto" national language usually evolves. English is the most common official language, with recognized status in 51 countries. Arabic, French, and Spanish are also widely recognized. An official language that is also an indigenous language is called "endoglossic", one that is not indigenous is "exoglossic". An instance is Nigeria which has three endoglossic official languages. By this the country aims to protect the indigenous languages although at the same time recognising the English language as its lingua franca. Around 500 BC,
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