به اعتقاد شیعیان هر سوره قرآن جز سوره توبه با آیهٔ «به نام خداوند بخشنده مهربان» آغاز میشود. و اهل سنت فقط «بسم الله الرحمن الرحیم» سوره حمد را جزء سوره میدانند.در قرآن این کلمه به همین معنا به کار رفتهاست. مثلاً در آیه تحدی (هماوردجویی) (بقره، ۲۳)
قرآن ۱۱۴ سوره دارد. هر سوره یک یا دو نام دارد، که معمولاً از کلمهای از آن سوره گرفته شدهاست. برخی معتقدند ترتیب سورهها توسط پیامبر تعیین شده و برخی بر این باورند که آنها به هنگام گردآوری در زمان عثمان کما بیش به ترتیب طول مرتب شدهاند. سورههای قرآن به دو دسته مکی (فرو فرستاده شده در مکه) و مدنی (فروفرستاده شده در مدینه) تقسیم میشوند. سورهها لزوما وحدت موضوعی ندارند. عایشه این مهم را اینطور تشریح میکند که اگر ابتدا حرمت خمر و زنا مطرح شده بود کسی مسلمان نمیشد، پس ابتدا آیات مربوط به بهشت و جهنم مطرح میشوند و پس از مسلمان شدن اصحاب باقی آیهها میآیند. (صحیح بخاری ۶-۵۱۵)
بخاری از قول عمر نقل میکند که وقتی عمر نسخه متفاوتی از سوره فرقان را میشنود، محمد به او میگوید که هر سوره هفت صورت جداگانه دارد. (صحیح بخاری ۶-۵۱۴)
سوره های قرآن از نظر کمی به چهار دسته تقسیم می شوند .
۱ - السبع الطول: عبارت از هفت سوره بزرگ قرآن یعنی:
بقره – آل عمران – نساء – مائده – انعام – اعراف – انفال و توبه
که تمامی آنها مدنی و پس از سوره حمد بترتیب در اول قرآن آمده است
۲- مئین: سوره هایی که از یکصد آیه تشکیل شده است و ۱۴ سوره اند
از سوره یونس تا مؤمنون ( از سوره ۱۰ تا ۲۳ قرآن )
۳ – مثانی: سوره هایی که میان اعراب متداول بوده و در نمازها قرائت می شوند
تعداد آنها ۲۶ سوره اند از نور تا حجرات ( از ۲۴ تا ۴۹ )
۴– مفصلات: سایر سوره های قرآن از ق تا ناس جمعاً ۶۵ سوره ( سری ۵۰ تا ۱۱۴ )
این دسته از سوره ها نیز خود بر سه گونه اند .
طوال: از ق تا بروج ۳۶سوره
اوساط: متوسط از طارق تا بینه۱۳ سوره
A Surah (//; also spelled Surat, Sura; Arabic: سورة sūrah, plural سور suwar) is a chapter of the Qur'an. There are 114 chapters of the Qur'an, each divided into verses. The chapters or suras are of unequal length, the shortest chapter (Al-Kawthar) has only three ayat (verses) while the longest (Al-Baqara) contains 286 verses. Of the 114 chapters in the Qur'an, 86 are classified as Meccan, while 28 are Medinan. This classification is only approximate in regard to location of revelation; any chapter revealed after migration of Muhammad to Medina (Hijrah) is termed Medinan and any revealed before that event is termed as Meccan. The Meccan chapters generally deal with faith and scenes of the Hereafter while the Medinan chapters are more concerned with organizing the social life of the nascent Muslim community and leading Muslims to the goal of Dar al-Islam by showing strength. Except sura At-Tawba, all chapters or suras commence with 'In the Name of God, the Merciful, the Compassionate'. This formula is known as the basmala and denotes the boundaries between chapters. The chapters are arranged roughly in order of descending size therefore the arrangement of the Qur'an is neither chronological nor thematic. Suras (chapters) are recited during the standing portions (Qiyam) of Muslim prayers. Sura Al-Fatiha, the first chapter of the Qur'an, is recited in every unit of prayer and some units of prayer also involve recitation of all or part of any other sura.
The word sura was used at the time of Muhammad as a term with the meaning of a chapter or a portion of the Qur'an. This is evidenced by the appearance of the word sura in multiple locations in the Qur'an such as verse 24:1:"A sura that We have sent down and appointed, and We have sent down in it signs, clear signs, that haply you will remember." Its plural form suwar is also mentioned in the Qur'an: "Or do they say, He invented it? Say, "Then bring ten suwar like it and call upon whomever you can besides God, if you are truthful." Nöldeke following Buxtorf suggested that the word sura has similar root with the Hebrew word 'שורה' meaning a 'row'. Some took it as connected with the Arabic word 'Sur' meaning a 'wall'. Jeffery believes that it has a common origin with a Syriac word that means 'writing'.
Chronological vs Traditional order
Further information: History of the Qur'an
Chapters in the Qur'an are not arranged in the chronological order of revelation, and the precise order of authorship has eluded scholars. According to tradition, Muhammad told his companions the traditional placement of every Wahy as he revealed it, and Wm Theodore de Bary, an East Asian studies expert, describes that "The final process of collection and codification of the Qur'an text was guided by one over-arching principle: God's words must not in any way be distorted or sullied by human intervention. For this reason, no serious attempt, apparently, was made to edit the numerous revelations, organize them into thematic units, or present them in chronological order...". 
A number of medieval Islamic writers attempted to compile a chronologically ordered list of the chapters, with differing results. As no transmitted reports dating back to the time of Muhammad or his companions exists, their works necessarily represent the opinions of scholars, and none originates before the first quarter of the 8th century. One version is given in a 15th-century work by Abd al-Kafi, and is included in the chronological order given by the standard Egyptian edition of the Qur'an (1924). Another list is mentioned by Abu Salih, while a significantly different version of Abu Salih's is preserved in the book 'Kitab Mabani'. Yet another, from the 10th century, is given by Ibn Nadim.
A number of verses are associated with particular events which helps date them. Muhammad's first revelation was chapter 96 (year 609). Verses 16:41 and 47:13 refer to migration of Muslims which took place in the year 622. Verses 8:1-7 and 3:120-175 refer to battles of Badr (624) and Uhud (625) respectively. Muhammad's last pilgrimage is mentioned in 5:3 which occurred in 632, a few months before he died. This method is of limited usefulness because the Qur'an narrates the life of Muhammad or the early history of the Muslim community only incidentally and not in detail. In fact, very few chapters contain clear references to events which took place in Muhammad's life.
Theodor Nöldeke's chronology is based on the assumption that the style of the Qur'an changes in one direction without reversals. Nöldeke studied the style and content of the chapters and assumed that (1) later (Madinan) chapters and verses and are generally shorter than earlier (Meccan) ones (2) Earlier Meccan verses have a distinct rhyming style while later verses are more prosaic (prose-like). According to Nöldeke earlier chapters have common features: many of them open with oaths in which God swears by cosmic phenomena, they have common themes (including eschatology, creation, piety, authentication of Muhammad's mission and refutation of the charges against Muhammad), and some Meccan chapters have a clear 'tripartite' structure (for example chapters 45, 37, 26, 15, 21). Tripartite chapters open with a short warning, followed by one or more narratives about unbelievers, and finally address contemporaries of Muhammad and invite them to Islam. On the other hand, Madinan verses are longer and have a distinct style of rhyming and concern to provide legislation and guidance for the Muslim community.
Richard Bell took Nöldeke's chronology as starting point for his research, however, Bell did not believe that Nöldeke's criteria of style was important. He saw a progressive change in Muhammad's mission from a man who preached monotheism into an independent leader of a paramount religion. For Bell this transformation in Muhammad's mission was more decisive compared with Nöldeke's criteria of style. Bell argued that passages which mentioned Islam and Muslim or implied that Muhammad's followers were a distinct community were revealed later. He classified the Qur'an into three main periods: the early period, the Qur'anic period, and the book period. Richard bell worked on the chronology of verses instead of chapters. Underlying Bell's method for dating revelations is the assumption that the normal unit of revelation is the short passage and the passages have been extensively edited and rearranged.
Mehdi Bazargan divided the Qur'an into 194 independent passages preserving some chapters intact as single blocks while dividing others into two or more blocks. He then rearranged these blocks approximately in order of increasing average verse length. This order he proposes is the chronological order. Bazargan assumed that verse length tended to increase over time and he used this assumption to rearrange the passages.
Neal Robinson, an scholar of Islamic studies, is of the opinion that there is no evidence that the style of Qur'an has changed in a consistent way and therefore style may not always be a reliable indicator of when and where a chapter was revealed. According to Robinson, the problem of the chronology of authorship is still far from solved.
Names of chapters in the Qur'an
The verses and chapters when revealed to Muhammad in the Qur'an did not come with a title attached to them. Muhammad, as we find in some reports in hadith, used to refer to shorter chapters not by name, rather by their first verse. For example: Abu Hurairah quoted Muhammad as saying, "Al-Hamdu Lillahi Rabb il-`Aalameen" is the Mother of the Qur'an, the Mother of the Book, and the seven oft-repeated verses of the Glorious Qur'an.". We also find reports in which Muhammad used to refer to them by their name. For example, Abdullah bin Buraydah narrated from his father, "I was sitting with the Prophet and I heard him say, 'Learn Surat ul-Baqarah, because in learning it there is blessing, in ignoring it there is sorrow, and the sorceresses cannot memorize it."'
Arab tradition, similar to other tribal cultures of that time, was to name things according to their unique characteristics. They used this same method to name Qur'anic chapters. Most chapter names are found in hadith. Some were named according to their central theme, such as Al-Fatiha (The Opening) and Yusuf (Joseph), and some were named for the first word at the beginning of the chapter, such as Qaf, Ya-Sin, and ar-Rahman. Some suras were also named according to a unique word that occurs in the chapter, such as al-Baqara (The Cow), An-Nur (The Light), al-Nahl (The Bee), Az-Zukhruf (The Ornaments of Gold), Al-Hadid (The Iron), and Al-Ma'un (The Small Kindness).
Most chapter names are still used to this day. Several are known by multiple names: chapter Al-Masadd (The Palm Fibre) is also known as al-Lahab (The Flame). Sura Fussilat (Explained in Detail) is also known as Ha-Meem Sajda ("...it is a chapter that begins with Ha Mim and in which a verse requiring the performance of prostration has occurred.")
Coherence in the Qur'an
The idea of textual relation between the verses of a chapter has been discussed under various titles such as "nazm" and "munasabah" in literature of the Islamic sphere and 'Coherence', 'text relations', 'intertextuality', and 'unity' in English literature. There are two points of view regarding coherence of the verses of the Qur'an. In the first viewpoint each chapter of the Qur'an has a central theme and its verses are related. The second viewpoint considers some chapters of the Qur'an as collections of passages which are not thematically related. Chapters deal with various subjects, for instance chapter 99, which comprises only eight verses, is devoted exclusively to eschatology and chapter 12 narrates a story, while other chapters, in the same breath, speak of theological, historical, and ethico-legal matters. Chapters are known to consist of passages, not only verses. The borders between passages are arbitrary but are possible to determine. For example, chapter 54 may be divided into six passages:
The study of text relations in the Qur'an dates back to a relatively early stage in the history of Qur'anic studies. The earliest Qur'anic interpreter known to have paid attention to this aspect of the Qur'an is Fakhruddin al-Razi (d.1209 ). Fakhr Razi believed that text relation is a meaning that links verses together or mentally associates them like cause-effect or reason-consequence. He linked verse 1 of a chapter to verse 2, verse 2 to verse 3 and so on, and rejected traditionist interpretations if they contradicted interrelations between verses. Zarkashi (d.1392), another medieval Qur'anic exegete, admitted that relationships of some verses to other verses in a chapter is sometimes hard to explain, in those cases he assigned stylistic and rhetorical functions to them such as parenthesis, parable, or intentional subject shift. Zarkashi aimed at showing how important understanding the inter-verse relations is to understanding the Qur'an, however, he did not attempt to deal with one complete chapter to show its relations.
Contemporary scholars have studied the idea of coherence in the Qur'an more vigorously and are of widely divergent opinions. For example, Hamid Farrahi (d. 1930) and Richard Bell (d. 1952) have different opinions regarding coherence within chapters. Farrahi believed that the whole structure of the Qur'an is thematically coherent, which is to say, all verses of a chapter of the Qur'an are integrally related to each other to give rise to the major theme of the chapter and again all of the chapters are interconnected with each other to constitute the major theme of the Qur'an. According to Farrahi, each chapter has a central theme (umud or pillar) around which the verses revolve:
In contrast, Richard Bell describes the Qur'anic style as disjointed:
Arthur J. Arberry states that the chapters in many instances, as Muslims have been recognized from the earliest times, are of a 'composite' character, holding embedded in them fragments received by Muhammad at widely differing dates. However he disregards this 'fact' and views each chapter as an artistic whole. He believed that a repertory of familiar themes runs through the whole Qur'an and each chapter elaborates one of more, often many of, them.
Angelika Neuwirth is of the idea that verses in their chronological order are interrelated in a way that later verses explain earlier ones. She believes that Meccan chapters are coherent units.
Salwa El-Awa aims in her work to discuss the problem of textual relations in the Qur'an from a linguistic point of view and the way in which the verses of one chapter relate to each other and to the wider context of the total message of the Qur'an. El-Awa provides a detailed analysis in terms of coherence theory on chapters 33 and 75 and shows that theses two chapters cohere and have a main contextual relationship.
Gheitury and Golfam believe that the permanent change of subject within a passage in the Qur'an, or what they call non-linearity, is a major linguistic feature of the Qur'an, a feature that puts the Qur'an beyond any specific 'context' and 'temporality'. According to Gheitury and Golfam for the Qur'an there is no preface, no introduction, no beginning, no end, a reader can start reading from anywhere in the text.