I'm trying to write out an document of sorts though I need the word for "someone who warns". I've done a bit of searching but couldn't find anything.

I initially thought it was "warner" though it doesn't show up in the English dictionary and doesn't exactly sound right.

So I ask, what is the correct word if there even is one. If there isn't a correct word, what would be best to use as surely, "someone who warns" can't be?

  • 1
    Any particular kind of warning? Is their warning heeded or is it ignored?
    – A E
    Nov 21, 2014 at 13:50
  • @AE The warning would be something like, "This is against the rules". As for being heeded or ignored, it'd be unknown so let's assume both.
    – Spedwards
    Nov 21, 2014 at 13:54
  • OK. Is their warning justified or are they just taking the opportunity to be bossy? Are they an authority figure like a police officer or a teacher who has the power to enforce rules, or are they a peer?
    – A E
    Nov 21, 2014 at 13:55
  • Justified and in authority.
    – Spedwards
    Nov 21, 2014 at 13:58
  • 1
    Tricky. They could be 'cautioning' the person. (A 'caution' is a specific legal thing in police jargon though, here in the UK at least, so beware). 'Cautioner' is a word but not one I'd suggest using. I think I'd just rephrase it.
    – A E
    Nov 21, 2014 at 14:04

9 Answers 9



 1. One who admonishes; one who warns of faults, informs of
    duty, or gives advice and instruction by way of reproof or
    [1913 Webster]

 2. Hence, specifically, a pupil selected to look to the
    school in the absence of the instructor, to notice the
    absence or faults of the scholars, or to instruct a
    division or class.
    [1913 Webster]

 3. someone who gives a warning so that a mistake can be avoided
    [Collaborative International Dictionary of English]

Somebody has to warn kids not to steal the milk.

It has the same root as admonish but describes the person and their authority.

  • 3
    This meaning of monitor is obsolete.
    – ermanen
    Nov 22, 2014 at 2:09
  • 1
    It is old fashioned and not widely used, @ermanen, but not yet obsolete. "a person who admonishes, especially with reference to conduct." That is what hall monitors (en.wikipedia.org/wiki/Hall_monitor) do and why they have that name.
    – itsbruce
    Nov 22, 2014 at 2:40
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    @itsbruce: "Hall monitor" is a phrase and the meaning of monitor in that phrase is someone who watches over something, not someone who warns or admonishes.
    – ermanen
    Nov 22, 2014 at 2:44
  • 1
    Wrong. They don't just watch, they maintain order by enforcing rules and telling people how to behave or what they are doing to break the rules. Is part of the definition. Read again. You seem to be ignoring part of the definition to justify a preconception.
    – itsbruce
    Nov 22, 2014 at 2:48
  • 1
    @itsbruce: I didn't ignore anything. I thought it is fair to mention so people know it. Our word is "monitor" also, not "hall monitor". Monitor has a current meaning who watches over or in charge of something, and that meaning is implied in "Hall Monitor" too. The obsolete meaning of monitor that I meant is someone who warns of faults or admonishes. The second meaning in your answer sounds like the definition of hall monitor but there are other kind of monitors also. When maintaining order, they might warn people but it is not a definition, it can be just part of their duty.
    – ermanen
    Nov 22, 2014 at 3:04

A harbinger is

  • a person who goes ahead and makes known the approach of another; herald.
  • anything that foreshadows a future event; omen; sign: Frost is a harbinger of winter.
  • a person sent in advance of troops, a royal train, etc., to provide or secure lodgings and other accommodations.

If your "warner" is able to warn, but is not believed, then a classical reference to being a Cassandra might be in order.

  • 1
    I do like this word (wasn't me who voted you down) but in comments Spedwards has made clear that official, direct warnings are the context.
    – itsbruce
    Nov 21, 2014 at 16:00
  • (Thank you for pointing out Spedwards' comments, @itsbruce.) Although I was responding to the stated question, I think that both harbinger and Cassandra convey the notion of a warning or foreshadowing of a negative event.
    – rajah9
    Nov 21, 2014 at 16:16

Warner is a word and it appears in dictionaries. It sounds right to me. Warner Bros. makes it harder to search though.

One who warns or gives warning to others.


One who warns.


someone who gives a warning to others

[TFD] and [Vocabulary.com]

An example from a news article:

Müller is a warner. He warns against running Europe into the ground "out of convenience," merely for the purpose of preserving the euro, which, according to Müller, is much too strong for the weak countries in the south but too weak for the strong German economy.


It usually appears in religious contexts though and prophets are considered as a warner:

In other words, a messenger and prophet is a warner but a warner isn’t necessarily a messenger or prophet.


Warner can be used for objects too, like a warning system:

The helicopter's electronic warfare systems include a radar warning receiver, laser warning receiver, missile approach warner and chaff and flare dispensers.



Not a very common term, but close to what you are looking for:


  • one that forewarns

to forewarn :

  • to warn (someone) before something happens

also: premonitor:

  • One who, or that which, gives premonition, a warning in advance; a forewarning.

(from M-W)


I am not sure whether it sounds correct or not but i was able to find ADMONISHER as a one word substitute for someone who warns

  • 1
    I was tempted to suggest that but an admonishment isn't really quite the same thing as a warning, necessarily. IMO.
    – A E
    Nov 21, 2014 at 14:06
  • @ A E: Well thefreedictionary.com certainly does not think so. :thefreedictionary.com/_/dict.aspx?rd=1&word=Admonisher Nov 21, 2014 at 14:27
  • actually it kind of does. The connotation 'to reprove' is what I was thinking of. That's meaning 1 in the definition you linked to. A 'warning' doesn't have that implication of "telling them off".
    – A E
    Nov 21, 2014 at 14:31
  • But the more authoritative OED says "A person who admonishes someone (in various senses of the verb); an adviser, a rebuker."
    – A E
    Nov 21, 2014 at 14:40

Could you use watchdog? It focuses on the watching as opposed to the warning, so it might be a little off. If we're talking "watchdog agencies" though (my experience with the word), the warning is strongly implied.

  • 1
    Clever. But does a watchdog warn the person who will break the rules (which is what the OP wants) or the people who are protected by the rules?
    – itsbruce
    Nov 21, 2014 at 15:58
  • 1
    Both. Definitely both, in practice.
    – Gerger
    Nov 25, 2014 at 14:54

Some options: Greek oracle, like the Oracle of Delphi. Prophet or prophetess (aka Cassandra). Someone who warns of impending calamity.



In ancient days, these were soldiers assigned to the towers that surrounded the city walls. They warn of people approaching, most often, raiding parties. Sometimes, they are sent out to ask if the arriving party comes in peace or not if someone travels alone. Their function also includes identifying people who come near the walls, and relay the message to another person (usually a runner/messenger) to ask permission from authorities for entry. Sometimes, they sound a trumpet to warn the citizens within the walls about imminent danger, or provide another signal of what lies outside the walls.


My suggestion is a Sentry.

Admonish has the connotation of scolding, telling off. If the usage is someone who is on the lookout, then Sentry is more appropriate in my view.

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