The word(s) "monotheism" appears 283 time(s) in 267 verse(s) in Quran in Mohsin Khan translation.

(201) And he made it [i.e. La ilaha illallah (none has the right to be worshipped but Allah Alone)] a Word lasting among his offspring, (True monotheism), that they may turn back (i.e. to repent to Allah or receive admonition).

(202) And not an Ayah (sign, etc.) We showed them but it was greater than its fellow , and We seized them with torment, in order that they might turn [from their polytheism to Allah's religion (Islamic monotheism)].

(203) And he ['Îsa (Jesus), son of Maryam (Mary)] shall be a known sign for (the coming of) the Hour (Day of Resurrection) [i.e. 'Isa's (Jesus) descent on the earth]. Therefore have no doubt concerning it (i.e. the Day of Resurrection). And follow Me (Allah) (i.e. be obedient to Allah and do what He orders you to do, O mankind)! This is the Straight Path (of Islamic monotheism, leading to Allah and to His Paradise).

(204) And let not Shaitan (Satan) hinder you (from the right religion, i.e. Islamic monotheism). Verily, he (Satan) to you is a plain enemy.

(205) "Verily, Allah! He is my Lord (God) and your Lord (God). So worship Him (Alone). This is the (only) Straight Path (i.e. Allah's religion of true Islamic monotheism)."

(206) (It will be said to the true believers of Islamic monotheism): My worshippers! No fear shall be on you this Day, nor shall you grieve,

(207) (You) who believed in Our Ayat (proofs, verses, lessons, signs, revelations, etc.) and were Muslims (i.e. who submit totally to Allah's Will, and believe in the Oneness of Allah - Islamic monotheism).

(208) Then We have put you (O Muhammad صلى الله عليه و سلم) on a (plain) way of (Our) commandment [like the one which We commanded Our Messengers before you (i.e. legal ways and laws of the Islamic monotheism)]. So follow you that (Islamic monotheism and its laws), and follow not the desires of those who know not. (Tafsir At-Tabari).

(209) Or do those who earn evil deeds think that We shall hold them equal with those who believe (in the Oneness of Allah - Islamic monotheism) and do righteous good deeds, in their present life and after their death? Worst is the judgement that they make.

(210) Then, as for those who believed (in the Oneness of Allah - Islamic monotheism) and did righteous good deeds, their Lord will admit them to His Mercy. That will be the evident success.