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

(81) Raised high above ranks (or degrees), (He is) the Lord of the Throne (of Authority): by His Command doth He send the Spirit (of inspiration) to any of His servants he pleases, that it may warn (men) of the Day of Mutual Meeting,-

(82) warn them of the Day that is (ever) drawing near, when the hearts will (come) right up to the throats to choke (them); No intimate friend nor intercessor will the wrong-doers have, who could be listened to.

(83) A believer, a man from among the people of Pharaoh, who had concealed his faith, said: "Will ye slay a man because he says, 'My Lord is Allah'?- when he has indeed come to you with Clear (Signs) from your Lord? and if he be a liar, on him is (the sin of) his lie: but, if he is telling the Truth, then will fall on you something of the (calamity) of which he warns you: Truly Allah guides not one who transgresses and lies!

(84) But if they turn away, say thou: "I have warned you of a stunning Punishment (as of thunder and lightning) like that which (overtook) the 'Ad and the Thamud!"

(85) Thus have We sent by inspiration to thee an Arabic Qur'an: that thou mayest warn the Mother of Cities and all around her,- and warn (them) of the Day of Assembly, of which there is no doubt: (when) some will be in the Garden, and some in the Blazing Fire.

(86) Just in the same way, whenever We sent a warner before thee to any people, the wealthy ones among them said: "We found our fathers following a certain religion, and we will certainly follow in their footsteps."

(87) We sent it down during a Blessed Night: for We (ever) wish to warn (against Evil).

(88) We created not the heavens and the earth and all between them but for just ends, and for a Term Appointed: But those who reject Faith turn away from that whereof they are warned.

(89) Say: "I am no bringer of new-fangled doctrine among the messengers, nor do I know what will be done with me or with you. I follow but that which is revealed to me by inspiration; I am but a warner open and clear."

(90) Mention (Hud) one of 'Ad's (own) brethren: Behold, he warned his people about the winding Sand-tracts: but there have been warners before him and after him: "Worship ye none other than Allah: Truly I fear for you the Penalty of a Mighty Day."