The word "murk" is one of the key terms of the Qur'an that plays a significant role in knowing the worldview of the Qur'an. Perceiving the precise meaning of this word helps the audience of the Qur'an to comprehend the Qur'an. The data were collected by the documentary method and processed by the descriptive-analytical method. Due to its semantic connection with other key concepts such as polytheism, atheism, transgression, light and faith, this term has a wide semantic scope. The present article examines first the lexical meaning of murk, then the uses of this word in the Arabic literature of the pre-Islamic era and also the Qur’anic uses of this word. Darkness is the true meaning of murk, and other meanings such as: placing the object out of its place and blemishing the Truth are virtual uses. Murk in the pre-Islamic period has been used in the meanings of darkness, deep darkness, evil, ignorance and also has been used against justice. Murk has spread semantically in the language of the Qur'an and in addition to darkness, it has also referred to atheism, ignorance, negligence, polytheism, misguidance, Falsehood, night, query, doubt, sins, wombs, hypocrisy, hardship and the wrath of God.