The Qur’an is composed of 114 parts or surah of unequal length. Each part is called a surah in Arabic and each sentence or phrase of the Qur’an is called an aayah or ayath, literally ‘a sign.’ The Qur’an is divided into discrete units, referred to as ‘aayaath’ in English. These aayaath are not standard in length and where each begins and ends was not decided by human beings, but Allah. Each one is a discrete act of locution of closed signification, or ‘sign’, denoted by the word aayah in Arabic. All surahs, except one, begin with Bimillah hir-Rahman nir-Rahim, ‘I begin with the Name of Allah, the Entirely Merciful, Especially Merciful.’ Each Surah has a name that usually relates to a central theme within it. For example, the longest surah, Surah al-Baqara, or “The Cow”, is named after the story of Moses commanding the Jews to offer a sacrifice of a cow, which begins by Allah saying: “And remember Moses said to his people: ‘Allah commands that you sacrifice a cow.’” Qur’an Surah Baqrah 2:67
Since the various Surah are of various lengths, the Qur’an was divided by scholars of the first century after the death of the Prophet into thirty roughly equal parts, each part is called a juz’ in Arabic. This division of the Qur’an was done in order for people to memorize or read it in a more organized fashion, and it has no influence on the original structure, as they are mere marks on the sides of the pages denoting the part. In the month of fasting, Ramadan, one juz’ is usually recited every night, and the entire Qur’an is completed by the end of the month.