Each of the ethnic groups found in Burkina Faso has its own language, the language of the Mossi, is spoken by a great majority of the population and Dyula and Hausa are widely used in commerce. French, the official language, is used for all communication with other countries. About 1/2 of the population are animists, attaching great importance to ancestor worship. Islam exerts an increasing determine upon customs, and Muslims account for around 2/5 of the population.