In terms of writing systems, Ethiopia's principal orthography is the Ge'ez script. Employed as an abugida for several of the country's languages, it first came into usage in the sixth and fifth centuries BC as an abjad to transcribe the Semitic Ge'ez language. Ge'ez now serves as the liturgical language of the Ethiopian and Eritrean Orthodox Tewahedo Churches. Other writing systems have also been used over the years by different Ethiopian communities. These include Arabic script for writing some Ethiopian languages spoken by Muslim populations and Sheikh Bakri Sapalo's script for Oromo. Today, many Cushitic, Omotic, and Nilo-Saharan languages are written in Roman/Latin script.