The word(s) "warn" appears 150 time(s) in 135 verse(s) in Quran in Mohsin Khan translation.

(41) And to warn those (Jews, Christians, and pagans) who say, "Allah has begotten a son (or offspring or children)."

(42) And We send not the Messengers except as givers of glad tidings and warners. But those who disbelieve, dispute with false argument, in order to refute the truth thereby. And they treat My Ayat (proofs, evidence, verses, lessons, signs, revelations, etc.), and that with which they are warned, as a jest and mockery!

(43) And warn them (O Muhammad صلى الله عليه وسلم) of the Day of grief and regrets, when the case has been decided, while (now) they are in a state of carelessness, and they believe not .

(44) So We have made this (the Qur'an) easy in your own tongue (O Muhammad صلى الله عليه وسلم), only that you may give glad tidings to the Muttaqun (the pious - See V.2:2), and warn with it the Ludd (most quarrelsome) people.

(45) And thus We have sent it down as a Qur'an in Arabic, and have explained therein in detail the warnings, in order that they may fear Allah, or that it may cause them to have a lesson from it (or to have the honour for believing and acting on its teachings).

(46) Say (O Muhammad صلى الله عليه وسلم): "I warn you only by the revelation (from Allah and not by the opinion of the religious scholars and others). But the deaf (who follow the religious scholars and others blindly) will not hear the call, (even) when they are warned [i.e. one should follow only the Qur'an and the Sunnah (legal ways, orders, acts of worship, and the statements of Prophet Muhammad صلى الله عليه وسلم, as the companions of the Prophet صلى الله عليه وسلم did)] .

(47) Say (O Muhammad صلى الله عليه وسلم): "O mankind! I am (sent) to you only as a plain warner."

(48) Allah forbids you from it and warns you not to repeat the like of it forever, if you are believers.

(49) Blessed be He Who sent down the criterion (of right and wrong, i.e. this Qur'an) to His slave (Muhammad صلى الله عليه وسلم) that he may be a warner to the 'Alamin (mankind and jinn).

(50) And they say: "Why does this Messenger (Muhammad صلى الله عليه وسلم) eat food, and walk about in the markets (as we). Why is not an angel sent down to him to be a warner with him?