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

(41) Behold! We told thee that thy Lord doth encompass mankind round about: We granted the vision which We showed thee, but as a trial for men,- as also the Cursed Tree (mentioned) in the Qur'an: We put terror (and warning) into them, but it only increases their inordinate transgression!

(42) And We said thereafter to the Children of Israel, "Dwell securely in the land (of promise)": but when the second of the warnings came to pass, We gathered you together in a mingled crowd.

(43) We sent down the (Qur'an) in Truth, and in Truth has it descended: and We sent thee but to give Glad Tidings and to warn (sinners).

(44) (He hath made it) Straight (and Clear) in order that He may warn (the godless) of a terrible Punishment from Him, and that He may give Glad Tidings to the Believers who work righteous deeds, that they shall have a goodly Reward,

(45) Further, that He may warn those (also) who say, "Allah hath begotten a son":

(46) We only send the messengers to give Glad Tidings and to give warnings: But the unbelievers dispute with vain argument, in order therewith to weaken the truth, and they treat My Signs as a jest, as also the fact that they are warned!

(47) But warn them of the Day of Distress, when the matter will be determined: for (behold,) they are negligent and they do not believe!

(48) Say: "If any men go astray, (Allah) Most Gracious extends (the rope) to them, until, when they see the warning of Allah (being fulfilled) - either in punishment or in (the approach of) the Hour,- they will at length realise who is worst in position, and (who) weakest in forces!

(49) So have We made the (Qur'an) easy in thine own tongue, that with it thou mayest give Glad Tidings to the righteous, and warnings to people given to contention.

(50) "But speak to him mildly; perchance he may take warning or fear (Allah)."