Eritrea's population comprises nine ethnic groups, most of which speak Semitic or Cushitic languages. The Tigrinya and Tigre make up four-fifths of the population and speak different, but related and somewhat mutually intelligible, Semitic languages. In general, most of the Christians live in the highlands, while Muslims and adherents of traditional beliefs live in lowland regions. Tigrinya and Arabic are the most frequently used languages for commercial and official transactions, but English is widely spoken and is the language used for secondary and university education.