Tawheed is the most important Islamic beliefs. It implies that everything in existence originates from the one and only creator and is also the sustainer and the sole source of guidance. This belief should govern all aspects of human life. Recognition of this fundamental truth results in a unified view of existence. Allah is the sole source of power and authority, therefore entitled to worship and obedience from mankind. There is no scope for any partnership with the creator. Tawheed tells man that Allah is not born, nor is anyone born of him. He has no son or daughter. Human beings are his subjects.
Linguistically Tawheed means: "To make something one or to assert the oneness of something." Technical meaning of Tawheed is: "To single out Almighty God alone for worship." Literally Tawheed means "unification" (making something one) or "asserting oneness", and 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 Allah’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" (sharing); the association of partners with Allah, which, in Islamic terms, is in fact idolatry.