The Quran consists of 114 chapters of varying lengths, each known as a sura. Suras are classified as Meccan or Medinan, depending on whether the verses were revealed before or after the migration of Muhammad to the city of Medina. However, a sura classified as Medinan may contain Meccan verses in it and vice versa. Sura titles are derived from a name or quality discussed in the text, or from the first letters or words of the sura. Suras are arranged roughly in order of decreasing size. The sura arrangement is thus not connected to the sequence of revelation. Each sura except the ninth starts with the Bismillah (بسم الله الرحمن الرحيم), an Arabic phrase meaning "In the name of God". There are, however, still 114 occurrences of the Bismillah in the Quran, due to its presence in Quran 27:30 as the opening of Solomon's letter to the Queen of Sheba.
Each sura consists of several verses, known as ayat, which originally means a "sign" or "evidence" sent by God. The number of verses differs from sura to sura. An individual verse may be just a few letters or several lines. The total number of verses in the Quran is 6,236; however, the number varies if the bismillahs are counted separately.
In addition to and independent of the division into suras, there are various ways of dividing the Quran into parts of approximately equal length for convenience in reading. The 30 juz' (plural ajzāʼ) can be used to read through the entire Quran in a month. Some of these parts are known by names—which are the first few words by which the juzʼ starts. A juz' is sometimes further divided into two ḥizb (plural aḥzāb), and each hizb subdivided into four rubʻ al-ahzab. The Quran is also divided into seven approximately equal parts, manzil (plural manāzil), for it to be recited in a week.
A different structure is provided by semantical units resembling paragraphs and comprising roughly ten ayat each. Such a section is called a rukū`.
The Muqattaʿat (Arabic: حروف مقطعات ḥurūf muqaṭṭaʿāt "disjoined letters" or "disconnected letters"; also "mysterious letters") are combinations of between one and five Arabic letters figuring at the beginning of 29 out of the 114 surahs (chapters) of the [Quran just after the basmala. The letters are also known as fawātih (فواتح) or "openers" as they form the opening verse of their respective suras . Four surahs are named for their muqatta'at, Ṭāʾ-Hāʾ, Yāʾ-Sīn, Ṣād and Qāf. The original significance of the letters is unknown. Tafsir (exegesis) has interpreted them as abbreviations for either names or qualities of God or for the names or content of the respective surahs.
According to one estimate the Quran consists of 77,430 words, 18,994 unique words, 12,183 stems, 3,382 lemmas and 1,685 roots.