TAWHÎD - توحيد‎

Literally and Etymologically:

Literally, it means oneness, declaration of unity, or making something one. Etymologically, it derives from the verbal root w-h-d (و-ح-د), denoting the deliberate act of asserting, affirming and declaring the absolute singularity and oneness of something.

As an Islamic Term:

It is the foundational belief of Islam, absolute monotheism, affirming Allah's absolute unity and uniqueness as the sole Creator and Sustainer of the entire universe, along with the declaration of that faith through the sacred statement of tawhîd: لاَ اِلهَ اِلاَّ اللّٰهُ. The essence of tawhîd is to know, comprehend and accept that causes are created merely as a veil of Allah’s Glory, Grandeur and Majesty to human reason, while possessing no real creative effect or ultimate authority over creation, and to act upon this foundational truth in every aspect of life. It stands as the absolute and uncompromising opposite of shirk.

(For further explanation, please refer to The Twenty-Second Word, The Twenty-Third Flash and The Thirty-Third Word.)