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

(91) Behold, We turned towards thee a company of Jinns (quietly) listening to the Qur'an: when they stood in the presence thereof, they said, "Listen in silence!" When the (reading) was finished, they returned to their people, to warn (them of their sins).

(92) We have truly sent thee as a witness, as a bringer of Glad Tidings, and as a warner:

(93) But they wonder that there has come to them a warner from among themselves. So the Unbelievers say: "This is a wonderful thing!

(94) The Companions of the Wood, and the People of Tubba'; each one (of them) rejected the messengers, and My warning was duly fulfilled (in them).

(95) And the Trumpet shall be blown: that will be the Day whereof warning (had been given).

(96) He will say: "Dispute not with each other in My Presence: I had already in advance sent you warning.

(97) We know best what they say; and thou art not one to overawe them by force. So admonish with the Qur'an such as fear My warning!

(98) Hasten ye then (at once) to Allah: I am from Him a warner to you, clear and open!

(99) And make not another an object of worship with Allah: I am from Him a warner to you, clear and open!

(100) This is a warner, of the (series of) warners of old!