Zambia has 10 indigenous languages (or language groups) spoken as a mother tongue by more than 1% of the population, four of which are each spoken by large segments of the population:
Bemba, Lozi, Nyanja, Tonga.
Bemba is widely used by non-native-speakers as a lingua franca in urban areas, especially on the Copperbelt. The full name of this language is Ichi-Bemba.
Nyanja (or Chi-Nyanja) is widely used by non-native-speakers as a lingua franca in urban areas, especially in the capital city of Lusaka. This language is also known as Chi-Chewa, especially in Zambia's Eastern Province and in Malawi, where it has the status of national language.
The other indigenous Zambian language groups are:
Kaonde, Lunda, Luvale, Mambwe-Namwanga, Nsenga,Tumbuka.
Each of these groups includes a number of dialects with fairly high mutual intelligibity.
The definitive source for research on Zambian languages is:
Ohannessian, S.I. & Kashoki, M.E. (Eds.) (1978) Language in Zambia.
London : International African Institute/University of Zambia.
This is currently out of print, but is being reprinted for reissue later in 2008 by the UNZA Press.
A more accessible summary publication is:
Banda, F. (1998). The classification of Languages in Zambia and Malawi.
CASAS Occasional Paper No. 1. Cape Town, South Africa: Centre for Advanced Studies
of African Society (CASAS). (ISBN No.1-919799-02-8)
(This can be ordered by email from CASAS at : firstname.lastname@example.org)
(June 2008 price: US $ 5 + $ 1 for postage)