There is not one Arabic text of the Qur'an but many variant readings exist. Some of these variant systems of reading have been "canonized" and there are several groups of readers (qurra') whose reading of the is accepted by Islamic scholarship. The most authoritative group are "The Seven Readers". Next in authority come "The Three" and together they make "The Ten Readers", but others recognize further four readers. Most of these readers are in turn supported by two transmitters. The following table gives an overview:
| THE ACCEPTED READERS AND THEIR TRANSMITTED VERSIONS OF THE QUR'AN | |
|---|---|
| "The Seven" | |
| Nafi` | Warsh |
| Qalun | |
| Ibn Kathir | al-Bazzi |
| Qunbul | |
| Abu `Amr al-'Ala' | al-Duri |
| al-Suri | |
| Ibn `Amir | Hisham |
| Ibn Dhakwan | |
| Hamzah | Khalaf |
| Khallad | |
| al-Kisa'i | al-Duri |
| Abu'l-Harith | |
| Abu Bakr `Asim | Hafs |
| Ibn `Ayyash | |
|
"The Three" | |
| Abu Ja`far | Ibn Wardan |
| Ibn Jamaz | |
| Ya`qub al-Hashimi | Ruways |
| Rawh | |
| Khalaf al-Bazzar | Ishhaq |
| Idris al-Haddad | |
|
"The Four" | |
| Muhaysin | ? |
| al-Yazidi | ? |
| al-Hasan al-Basri | ? |
| al-A`mash | ? |
More details about this topic (dates, geographic distribution, etc.) is provided in the article The Different Arabic Versions of the Qur'an.
These readers / readings are still not covering all the variant readings of the Qur'an that exist. These are only the canonical ones. The overview page The Text of the Qur'an provides further details (see particularly section 9. of this page).
Sometimes the different readings can be found even in English translations, cf. Books or People? - The Variant Readings of Surah 28:48.