The term Shi'ah literally means "follower" or "partisan" and it has also been used to mean "path", "faction", or a "member of a party". In the technical sense, the term Shi'ah has as close connection with the followers of the Commander of the Faithful, Ali (a.s.). It has been used to refer to the followers, lovers and partisans of Ali (a.s.) or those who consider Ali (a.s.) superior to Uthman, or those who consider him superior to Utman and the first two caliphs and all other companions of the Holy Prohpet (s). Also, this term refers to those who believe in the immediate successorship of Imam Ali (a.s.) to the Holy Prophet (s). However, the best definition for this term is to say: "Shi'ah is one who considers Ali's rightful successorship to the Prophet (s) proven through textual evidence and believes that Ali (a.s.) is the worthiest person to succeed the Holy Prophet (s).
The term "Shi'ah" is a vas and inclusive concept which according to the accepted definition includes all Shi'ah sects and branches such as Zaydiyah, Kisaniyah, Ismailiyah etc.
The followers of Ahlul-Bayt (a.s) are also referred to with terms such as Ja'fari, Khassah, Alawi, Fatimi, Imami etc.
There are several opinions about the main branches Shi'ah Islam. Some have considered the basic Shi'ah sects to be Zaydiyah, Kisaniyah and Imamiyah whereas Shahristani have also included Ismailiyah among the major Shi'ah sects. In his Qawa'edul Aqaid, Khajah Tusi (r.a) has agreed with what has been said by Baghdadi. Thus he also believes that Shi'ah is basically divided into three main branches. The popular and widely accept opinion among Shi''ah scholars and historiographers is that the main Shi'ah sects are Zaydiyah, Kisaniyah and Imamiyah but the discrepancy exists as to the sub-sects and their branches.
The term Shi'ah literally means "follower" or "partisan" and it has also been used to mean "path" or a "member of a party".
In the technical sense, the term Shi'ah has as close link and connection with the followers of the Commander of the Faithfu, Ali (a.s.). It has therefore been used in diverse meanings such as the following:
1. Shi'ah in the sense of "lovers" and "partisans" of Imam Ali (a.s).
2. Shi'ah refers to those who consider Ali bin Abi Talib (a.s.) superior to Uthman. Thus, there are the partisans of Ali (a.s) against the partisans of Uthman.
3. Shi'ah refers to those who consider Ali (a.s.) superior to Utman and to the first two caliphs and all other companions of the Holy Prophet (s).
4. Also, this term refers to those who believe in the immediate successorship of Imam Ali (a.s.) to the Holy Prophet (s).
None of the above definitions is inclusive and exclusive. Considering that there are different Shi'ah sects, perhaps the best definition for the term "Shi'ah" is to say: "Shi'ah is one who considers Ali's successorship substantiated through textual evidence (i.e. evidence from the Quran and written Prophetic tradition) and believes that Ali (a.s.) is the worthiest person for the successorship of the Holy Prophet (s)." In this definition, emphasis has been laid on 'textual evidence' [nas] which is the point of distinction between Shi'ah and other religious denominations. That is because other denominations believe that the Holy Prophet's successor was chosen by a council of elites but Shi'ah believes that the Prophet (s) himself appointed his successor and that there are numerous narrations where the Holy Prophet (s) selected Ali (a.s) as the next rightful caliph after him.
The Origin and Early Development of Shi'ism
Some researchers have said that Shi'im came into being after the demise of the Holy Prophet (s). They have also been divided into few groups:
One group says: Shi'ism came into being on the day of Saqifah. It is the day in which a group of the prominent companions of the Prophet (s) declared that Ali is more appropriate for authority, Imamate and caliphate.
Another group says that Shi'ah emerged in the closing period of Uthman's caliphate; they consider the spread of Abdullah bin Saba's view in this time to have some relation with the emergence of Shi'ism.
A third group says that Shi'ah came into being on the day of Fitnat al-Dar (the day of the third caliph's murder).
There is a fourth group which says that Shi'ism came into being following the event of Hakamiyah (arbitration) until the martyrdom of Imam Ali (a.s).
A fifth group views that the origin of Shi'ah dates back to the movement of Karbala and the martyrdom of Imam Hussein (a.s).
Contrary to all the foregoing diverse and scattered views about the origin and development of Shi'ah Islam, there are some researchers who believe that Shi'ism originated in the period of the Holy Prophet (s) who many a time, used this term about the followers and friends of the Commander of the Faithful, Ali (a.s.). Among the Shi'ah scholars late Kashif al-Ghita, Shaykh Muhammad Hussein Muzaffar, Muhammad Hussein Zayn Amili and among the Sunni scholars Muhammad Kurd Ali say: "Some of the companions during the time of Holy Prophet (s) were known as the Shi'ah of Ali (a.s.).
The term "Shi'ah" is a vast and inclusive concept which according to the accepted definition includes all Shi'ah sects and branches such as Zaydiyah, Kisaniyah, Ismailiyah etc. However, there are also some other terms which are somehow different with this common concept some of which are ascribed to the followers of Ahlul-Bayt (a.s). It is therefore necessary that we give a short explanation concerning each of these terms. Some of these terms are the following:
1. Rafidhi: Rafdh means denial, refusal, rejection, repudiation etc. Those who are hostile to Shia are using this term to denounce and revile Shi'ah. It has been said in connection with this term: "Since the Shiites rejected the caliphate of the first two caliphs, they are Rafidhis." Some have also said that the term "Rafidhi" refers to Shiites who because of their lenient stance towards the first two caliphs, left their camps. Whichever of these terms we accept, the term "Rafidhi" is not synonymous with "Shi'ah" in its common and broad sense because this term does not include some groups of the Zaydiyah sect.
2. Ja'fari: Given the fact that Imam Ja'far Sadiq (a.s) gave, through great efforts, a special jurisprudential and theological identity to the Shiites who believed in the leadership of the Infallible Imams (a.s), the Shiites who were benefitted by his teachings were known as Ja'fari. Today, the term "Ja'fari" is synonymous with "Shi'ah Ithna Ashari" but it also essentially includes the Ismailis because they also believe in the Imamate of Imam Ja'far Sadiq (a.s).
3. Imami: Imami is a reference to those Shiites who believed in the Imamate of twelve Infallible Imams from the descendants of Fatima, the daughter of the Holy Prophet (s.a). In the course of its development in history, depending on various times and occasions, since the term had been synonymous with Shi'ah in the time of Imam Ali (a.s.), today it has the same meaning as Shi'ah Ithna Ashari.
4. Khassa: This term is more often used in jurisprudential texts and it refers to Shiites as opposed to Ammah (the majority Sunni Muslim). A more special meaning of this term has been used in the jurisprudential texts of Shi'ah Ithna Ashari which takes its Fiqh (jurisprudence) from the twelve Infallible Imams (a.s.).
5. Alawi: Perhaps this term at times denoted the theological tendency of Shi'ah (belief in Imam Ali's superiority), but it has been used more or less to indicate the relative affiliation and attachment of a group of people towards Ali bin Abi Talib (a.s).
6. Fatimi: This term is used in a relative meaning and it is used more often to indicate a distinction between the descendants of Imam Hasan and Imam Hussein (a.s.) and those of Muhammad Hanafiyah to whom "Kisaniyah" relates itself because Muhammad Hanafiyah was not Fatima Zahra's son, though he is included among Imam Ali's sons.
7. Talibi: This term also has a relative a meaning but it is more exhaustive and broader than the two previous terms. Talibi means the children of Abu Talib who had children other than Ali (a.s) also. A precise and clear understanding of this term can be reached through Maqatil al-Talibeen by Abul Faraj Esfahani in which the author has provided a detailed account of the Talibis including those of the children of Ja'far bin Abi Talib.
These are the various terms used over the history to make reference to Shi'ah.
Shi'ism has been through ups and downs over its turbulent history. At times, it has been on the verge of taking over the entire Islamic world and at other times, it has been going down towards complete destruction. Meanwhile, what has made this school distinct from other religious schools are elements such as a rich past (history) in various aspects of Islamic teachings, the claim that it can establish a government (and it has proved so far at different time periods that it can establish such a government) and finally the independent identity of Shi'ism over the history. Given the fact that Shi'ah enjoys strong rational, jurisprudential, theological and moral support, it has been able, despite all the restrictions, pressures and poisonous propaganda launched against it, to spread across the world with its followers increasing day by day. Unfortunately, we must confess that the widespread threat of discord and creation of multiple splits facing the religions and denominations is also challenging Shi'ism to some extent. We hope that with the increasing awareness among Muslims and true followers of the Holy Prophet (s) and the Ahlul-Bayt (a.s), Muslims will come together, unite and defeat the enemies and put aside all the deviant religions and converge under the standard of one true religion.
When it comes to the number of basic Shi'ah sects, there are few opinions in this regard:
Baghdadi believes that the basic Shi'ah sects are Zaydiyah, Kisaniyah and Imamiyah. In beginning, he also considered Ghulat as one of the Shi'ah branches but then he says that they have gone out of Islam and they are not considered to be among the Islamic sects.
Shahristani has also included Ismailiyah among the major Shi'ah sects. He believes that there are five major sects in Shi'ah.
In his Qawa'edul Aqaid, Khajah Tusi (r.a) has agreed with what has been said by Baghdadi. Thus he also believes that Shi'ah is basically divided into three sects. Qazi 'Azud al-Deen Eyji also believes that the basic Shi'ah sects are three: Kisaniyah, Imamiyah and Zaydiyah.
Some other scholars also hold that Shi'ah consists of four basic sects such as Imamiyah, Kisaniyah, Zaydiyah and Ismailiyah.
The popular and widely accept opinion among Shi''ah scholars and historiographers is that the major and basic Shi'ah sects are Zaydiyah, Kisaniyah and Imamiyah but the discrepancy exists about the sub-sects and their branches.
For further information in this regard vide: Al-Farq bayn al-Fefraq, Melal wa Nehal, Qawa'ed al-Aqaid.
1. Shi'ah Branches (Inshi'abat Shi'ah)
2. Getting to Know Shi'ah (Ashnai ba Shi'ah)
 - Al-Qamoos Al-Mohit, vol.3, pg. 61 and 62; Taaj al-Arus, vol.5, pg. 405; Lisan al-Arab, vol.5, pg. 258; Al-Nihayah Ibn Athir, vol.2, pg. 246.
 - See: History of Shi'ism in Iran by Rasul Ja'fariyan, pg. 24-28.
 - Al-Farq bayn al-Feraq, Baghdadi, Abdul Qahir, p.g 21-23.
 - Melal wa Nehal, Shahristani, vol.1, pg. 147.
 - Tusi, Khaja Nasir, Qawa'ed al-Aqaid, researched by Rabbani, Ali, pg.110.