Tauhid
From Mw
Tauhid (Arabic: توحيد )is the Islamic concept of monotheism In Islam, Tauhīd means to assert the unity of God. It comes from the Arabic verb (wahhada) which itself means to unite, unify or consolidate.However, when the term Tawheed is used in reference to Allah (i.e. Tawheedullaah), it means the realizing and maintaining of Allaah's unity in all of man's actions which directly or indirectly relate to Him. It is the belief that Allah is One, without partner in His dominion and His actions (Ruboobeeyah), One without similitude in His essence and attributes (Asmaa wa Sifaat), and One without rival in His divinity and in worship (Ulooheeyah 'Ebaadah). These three aspects form the basis for the categories into which the science of Tawheed has been traditionally divided. The three overlap and are inseparable to such a degree that whoever omits any one aspect has failed to complete the requirements of Tawheed. The omission of any of the above mentioned aspects of Tawheed is referred to as "Shirk" (lit. sharing); the association of partners with Allah, which, in Islamic terms, is in fact idolatry.
[edit] Where the divisions of Tawheed come from
The division of Tawheed into its components was not done by the Prophet 
nor by his companions, as there was no necessity to analyze such a basic principle of faith in this fashion. However, the foundations of the components are all implied in the verses of the Qur'an and in the explanatory statements of the Prophet and his companions
