Caliphate is a legal requirement and Islam approves no other political system but it; it is the only accepted system for ruling in Islam.
• Linguistically, the word "caliphate" is derived from khalafahu, that is, to succeed someone; yukhlifuhu, that is, he makes him his successor or the caliph i.e. a person appointed as the forthcoming successor by the current ruler.
• Technically, it means administering the affairs of people in this worldly life according to the Shariah of Allah.
• The first and foremost task of caliphate is to administer the affairs of this worldly life guided by the teachings of religion and to preserve and disseminate religion. So, whoever claims to be a caliph without fulfilling his due duties, he is a liar.
• In the Islamic perspective, caliphate is a political system that is not meant for itself rather it focuses mainly on specific objectives and outcomes; so, other titles may be coined to it.
• Linguistically, the word Khaliafa refers to any ruler that succeeds a previous one. Technically, it refers only to those rulers who followed the footsteps of the Prophet (PBUH) in managing the affairs of this world guided by the teachings of religion.
• Imam al-Tirmidhi, Imam al-Nasaa'i, Imam Abu Dawud and Imam Ahmed narrated that the Messenger of Allah (PBUH) said, "Caliphate will be in my Ummah for thirty years, then there will be monarchy after that."
The term "caliphate" in this Hadith refers specifically to the period of the Rightly Guided Caliphates of Abu Bakr, 'Umar, 'Uthman, 'Ali and al-Hasan ibn 'Ali, may Allah be pleased with all of them. As such, all the regimes that came into existence after these Rightly Guided Caliphates shall thus fall under the classification of kingship and not the religious caliphate inherited from the Messenger of Allah (PBUH). However, today's rulers may be called "caliphates" on a linguistic basis, because they succeeded other rulers in assuming the office of rule.