The Urdu alphabet is the right-to-left alphabet used for the Urdu language. It is a modification of the Persian alphabet, which is itself a derivative of the Arabic alphabet. With 38 letters and no distinct letter cases, the Urdu alphabet is typically written in the calligraphic Nastaʿlīq script, whereas Arabic is more commonly in the Naskh style. Usually, bare transliterations of Urdu into Roman letters (called Roman Urdu) omit many phonemic elements that have no equivalent in English or other languages commonly written in the Latin script. The National Language Authority of Pakistan has developed a number of systems with specific notations to signify non-English sounds, but these can only be properly read by someone already familiar with the loan letters.