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

(121) Arise and deliver thy warning!

(122) And We have set none but angels as Guardians of the Fire; and We have fixed their number only as a trial for Unbelievers,- in order that the People of the Book may arrive at certainty, and the Believers may increase in Faith,- and that no doubts may be left for the People of the Book and the Believers, and that those in whose hearts is a disease and the Unbelievers may say, "What symbol doth Allah intend by this?" Thus doth Allah leave to stray whom He pleaseth, and guide whom He pleaseth: and none can know the forces of thy Lord, except He and this is no other than a warning to mankind.

(123) A warning to mankind,-

(124) Whether of Justification or of warning;-

(125) Verily, We have warned you of a Penalty near, the Day when man will see (the deeds) which his hands have sent forth, and the Unbeliever will say, "Woe unto me! Would that I were (metre) dust!"

(126) Verily in this is an instructive warning for whosoever feareth (Allah).

(127) Thou art but a warner for such as fear it.

(128) Therefore do I warn you of a Fire blazing fiercely;