Several writers have discussed the concept of national language (Fishman, 1968a; Le Page, 1964; Nida and Wonderly, 1971) but I should like here to follow Heine (1979) where he differentiates three types of national language:
(1) The de jure national language. In this case the national language has been officially chosen by governmental decree. Thus, for example, Tanzania elected Swahili its national language in 1961. Namibia has three national languages: Afrikaans, English and German, and Nigeria has nine. It is interesting that of the 46 African states only 22 have an "official" national language.
(2) The de facto national language. This "unofficial" national language must fulfill two of the following criteria:
(a) it must be used as a spoken medium throughout the nation and be spoken by more than half the population;
(b) the language must symbolize national unity or identity;
( c) the language must be considered as a means of expressing national culture and the national way of life.
An example of the de facto national language would be the Wolof language in Senegal.
(3) The de jure and de facto national language. Examples of an "official" national language with a firm numerical base are Swahili in Tanzania, Somali in Somalia and Arabic in Algeria.