In Islam, Qirāah, (pl. Qirāāt; قراءات ) are different linguistic, lexical, phonetic, morphological and syntactical forms permitted with reciting the holy book of Islam, the Quran. Differences between Qiraat are slight and include varying rules regarding the prolongation, intonation, and pronunciation of words, but also differences in stops, vowels, consonants (leading to different pronouns and verb forms), and less frequently entire words. Qiraʼat also refers to the branch of Islamic studies that deals with these modes of recitation. There are ten recognised schools of qiraat, each one deriving its name from a noted Quran reciter or "reader" (qāriʾ pl. qāriʾūn or qurr'aʿ), such as Nafi‘ al-Madani, Ibn Kathir al-Makki, Abu Amr of Basra, Ibn Amir ad-Dimashqi, Aasim ibn Abi al-Najud, Hamzah az-Zaiyyat, and Al-Kisa'i. While these readers lived in the second and third century of Islam, the scholar who approved the first seven qira'at (Abu Bakr Ibn Mujāhid) lived a century later, and the readings themselves have a chain of transmission (like hadith) going back to the time of Muhammad. Consequently, the readers/qurr'aʿ who give their name to Qira'at are part of a chain of transmission called a riwaya. The lines of transmission passed down from a riwaya are called turuq, and those passed down from a turuq are called wujuh. Qiraat should not be confused with Tajwid—the rules of pronunciation, intonation, and caesuras of the Quran. Each Qira'ah has its own tajwid. Qiraat are called readings or recitations because the Quran was originally spread and passed down orally, and though there was a written text, it did not include most vowels or distinguish between many consonants, allowing for much variation. (Qiraat now each have their own text in modern Arabic script.) Qira'at are also sometimes confused with Ahruf—both being readings of the Quran with "unbroken chain(s) of transmission going back to the Prophet". There are multiple views on the nature of the ahruf and how they relate to the qira'at, the general view being that caliph Uthman eliminated all of the ahruf except one during the 7th century CE.