The word(s) "warn" appears 140 time(s) in 128 verse(s) in Quran in Abdullah Yusuf Ali translation.

(111) "So taste ye My Wrath and My warning."

(112) To the People of Pharaoh, too, aforetime, came warners (from Allah).

(113) It is He Who got out the Unbelievers among the People of the Book from their homes at the first gathering (of the forces). Little did ye think that they would get out: And they thought that their fortresses would defend them from Allah! But the (Wrath of) Allah came to them from quarters from which they little expected (it), and cast terror into their hearts, so that they destroyed their dwellings by their own hands and the hands of the Believers, take warning, then, O ye with eyes (to see)!

(114) Almost bursting with fury: Every time a Group is cast therein, its Keepers will ask, "Did no warner come to you?"

(115) They will say: "Yes indeed; a warner did come to us, but we rejected him and said, 'Allah never sent down any (Message): ye are nothing but an egregious delusion!'"

(116) Or do ye feel secure that He Who is in Heaven will not send against you a violent tornado (with showers of stones), so that ye shall know how (terrible) was My warning?

(117) But indeed men before them rejected (My warning): then how (terrible) was My rejection (of them)?

(118) Say: "As to the knowledge of the time, it is with Allah alone: I am (sent) only to warn plainly in public."

(119) We sent Noah to his People (with the Command): "Do thou warn thy People before there comes to them a grievous Penalty."

(120) He said: "O my People! I am to you a warner, clear and open: