warn

Etymology

From Middle English warnen, warnien (“to warn; admonish”), from Old English warnian (“to take heed; warn”), from Proto-Germanic *warnōną (“to warn; take heed”), from Proto-Indo-European *wer- (“to be aware; give heed”). Cognate with Dutch waarnen (obsolete), German Low German warnen, German warnen, Swedish varna, Icelandic varna.

verb

1. (transitive) To make (someone) aware of (something impending); especially:
   1. (transitive) To make (someone) aware of impending danger, evil, etc.
      We waved a flag to warn the oncoming traffic about the accident.
      I phoned to warn him of the road closure.
   2. (transitive) To notify or inform (someone, about something).
      I warned him he'd be getting a huge box of birthday presents from me.
   3. (transitive) To summon (someone) to or inform of a formal meeting or duty.
      The sheriff warned her to appear in court.
      Committee being warned these following were absent or short … 1741–2 March 4, Books of Keelman's Hospital, Newcastle, quoted in Northumberland Words (1894)
      The people had been invited to the funeral, or warnt, by a special messenger a few days before the funeral took place. 1874, Walter Gregor, An Echo of the Olden Time from the North of Scotland, page 142
      … the plaintiff fraudulently warned the meeting for November 15, giving only five days' notice … 1889, Reports of Cases Argued and Determined in the Supreme Court of the [State of] Vermont, page 490
   4. (transitive, intransitive, of a clock, possibly obsolete) To make a sound (e.g. clicking or whirring) indicating that it is about to strike or chime (an hour).
      Hark! the clock is warning ten; 1885, Walter Towers, Poems, Songs, and Ballads, page 189
      No, not a word more, Andrew; the clock has warned for nine, and I am off. 1885, Emma Marshall, In the East Country with Sir Thomas Browne, page 106
      The clock warned, and the hands pointed to a few minutes before the hour. The preacher looked towards it. "And, as you sit here," he cried," the Old Year is dragging out its last moments and the New Year is coming up —" 1902, Violet Jacob, The Sheep-Stealers, page 399
2. (transitive) To caution or admonish (someone) against unwise or unacceptable behaviour.
   He was warned against crossing the railway tracks at night.
   Don't let me catch you running in the corridor again, I warn you.
3. (chiefly with "off", "away", and similar words) To advise or order to go or stay away.
   A sign warns trespassers off/away from the site.
4. (intransitive) To give warning.
   She is his deepest innocence in spaces of bough and hay before wishes were given a different name to warn that they might not come true …. 1973, Thomas Pynchon, Gravity's Rainbow, Penguin, published 1995, page 177
   She warned that he was seriously thinking of withdrawing his offer to part the waters, ‘so that all you'll get at the Arabian Sea is a saltwater bath …’. 1988, Salman Rushdie, The Satanic Verses, Picador, published 2000, page 496
   Every country has its resident experts who warn that imported television will destroy the national consciousness and replace it with Dallas, The Waltons, Star Trek and Twin Peaks. 1991, Clive James, “Making Programmes the World Wants”, in The Dreaming Swimmer, Jonathan Cape, published 1992