What's the difference between "vapour" and "mist"?

I ask because I was reading the Wikipedia article for Electronic Cigarettes and there is a lengthy and acrimonious discussion. I don't want to get involved! But I do want to know if there is a difference, and what it is.

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    Mist is typically deserved for water vapor, whereas vapor can be almost any substance. That said, vapor unqualified or otherwise unspecified is typically understood as water vapor by default; but the very existence of the phrase "water vapor" tells us it's sometimes necessary to specify or disambiguate. There is no such phrase as water mist to my knowledge. – Dan Bron Nov 18 '14 at 12:33
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    Have you looked up the words in a good dictionary? Let's know what you found. – Kris Nov 18 '14 at 14:22
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    @kris - This question is on topic for this site. I prefer to get good quality advice from this site where answerers will have a range of good quality dictionaries available, but who will also have ideas about etymology and usage. Online dictionaries are mostly useless. Do you have any that you'd recommend? (Your comment comes across as rude and unwelcoming. Did you realise that?) – DanBeale Nov 18 '14 at 20:02
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    @Kris is often blunt in comments. However, the question does not demonstrate any prior research. In fact, I'm very tempted to close it as General Reference, because as it stands it can surely be definitively answered by a couple of dictionaries. If it can't be, show that. It's not up to the community here to prove that it can be. Sorry. – Andrew Leach Nov 18 '14 at 22:57
  • @kris - that is a much better, much more useful, comment. Thanks. – DanBeale Nov 19 '14 at 18:05

Historically, mist was categorized as a meteorological or atmospheric condition. Hence, Webster's Dictionary of Synonyms (1942) lists mist in a category with haze, fog, smog, and brume:

Haze, mist, fog, smog, and brume agree in denoting an atmospheric condition which deprives the air near the earth of its transparency. ... Mist applies to a condition where water is held in suspension in fine particles in the air, floating or slowly falling in minute drops.

Figuratively, as Merriam-Webster's Eleventh Collegiate Dictionary (2003) observes, mist can also refer to various things suggestive of atmospheric mist:

4 a : a cloud of small particles or objects suggestive of a mist b : a suspension of a finely divided liquid in a gas c : a fine spray

In contrast, though vapor can be used to describe mistlike conditions, it has a stronger connection to gaseous rather than particulate solid or liquid states. It comes from the Latin word vapor meaning steam. Again from the Eleventh Collegiate, here are the first three definitions:

vapor n (14c) 1 : diffused matter (as smoke or fog) suspended floating in the air and impairing its transparency 2 a : a substance in the gaseous state as distinguished from the liquid or solid state b : a substance (as gasoline, alcohol, mercury, or benzoin) vaporized for industrial, therapeutic, or military uses; also : a mixture (as the explosive mixture in an internal combustion engine) of such vapor with air

Given the association of vapor with heating or sublimating into lighter than air gases (and leaving aside the stubborn fact that vapor has long been used as a way to describe fogs and—inevitably—mists), one might argue that a vapor in many instances rises, while a mist tends to descend slowly.

Incidentally, Noah Webster, in his Compendious Dictionary of the English Language (1806) gives only the heated or sublimated sense of vapor:

Vapor n. a fluid rendered volatile and elastic by heating, fume

Samuel Johnson, Dictionary of the English Language (1756) has a more varied (and interesting) take on the word:

VAPOUR. s. [vapor, Lat.] 1. Any thing exhalable ; any thing that mingles with the air. Milton. 2. Wind, flatulence. Bacon. 3. Fume ; steam. Newton. 4. Mental fume ; vain imagination. Hammond. 5. Diseases caused by flatulence, or by diseased nerves ; melancholy ; spleen. Addison.


I believe a mist is a vapour which can be seen.

A vapour is more scientifically descriptive of what it is, and it may be invisible to the eye.

I think the question of what substance gives rise to the mist or vapour is irrelevant.

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