One definition of zero is 2
the absence of a measurable quantity
However, this is a noun.
As an adjective , zero means not any or no Based on this definition, it is correct to use it to describe a mass noun to say there is none of it.
I've noticed that using "zero" instead of "no" is usually used to emphasize the lack of whatever it's describing.
ell.stackexchange.com/users/133/yoozer8
OED definitions include... Nought or nothing reckoned as a number denoted by the figure 0
That is of the amount expressed by zero, i.e. none at all; in Math.
also transf.
applied to a value of a function corresponding to the value 0 of the variable(s).
Hence ( colloq. )
more widely as adj.
in the sense ‘ no, not any ’.
[emphasis mine].
That's to say, by traditional definitions and usage
, OP is correct in saying that zero is a number - so it shouldn't be used as a quantifier , in contexts where you wouldn't use any other number.
But in fact it's commonly used that way colloquially (usually only in spoken informal contexts).
Having said that, there are restrictions on its use... ?
It's zero good hoping people will accept this as a reasonable utterance, even in casual speech.
Actually, I suppose it's possible some native speakers (certainly not me!
:)
will accept that contrived example.
But I'm betting the vast majority wouldn't, so my advice to learners would be to avoid the form completely and always use no instead.
You'll never be wrong that way.
ell.stackexchange.com/users/126/FumbleFingers Reinstate Monica
It's a rhetorical flourish.
The person who said zero courage is "bending the rules" of ordinary usage.
To a native speaker, saying zero as a synonym for no is a reasonable variation from normal usage.
The ordinary phrasing is no courage ; that would have drawn no attention to itself.
Saying zero courage is emphatic: it's like saying "There was not even a little bit of courage in this verdict.
There was no courage at all. "
While zero courage in this context doesn't sound ungrammatical or sloppy to most native speakers, there are very similar phrases that no native speaker would say because they break rather than bend ordinary usage.
For example, nobody would say two courage .
That would be incomprehensible.
See FumbleFingers' answer for another good example of going too far.
You shouldn't take the example as evidence contradicting the principle that mass nouns cannot be enumerated.
It's evidence that zero can sometimes be stretched into an intensified version of no .
There is no precise general rule for when you can and can't do this kind of thing.
You just have to get a sense of how far you can bend the language without breaking it.
That can only come with (long) experience.
ell.stackexchange.com/users/6700/Ben Kovitz
One of the possible meanings of zero is "the lowest possible amount or level; nothing at all"; one of the example phrases shown by the OALD is "zero inflation.
" The example is similar to yours, since both courage and inflation are uncountable.
ell.stackexchange.com/users/95/kiamlaluno
Some nouns like "courage" are quantifiable but not really measurable; one could describe Fred as having "more" courage than Joe, but there's no standard unit of courage that would make it possible to say that e.g. Fred has 2.7 more couragions than Joe.
The lack of defined units, however, doesn't affect "zero" because zero doesn't require units .
If something is has a length of zero inches, zero centimeters, and zero angstroms, or zero miles, it has zero length; the units don't matter.
If something has a mass of zero ounces, zero milligrams, or zero tons, it has zero mass; again, the units don't matter.
That principle can be extended to things like "courage": it's not possible to specify any particular non-zero quantity of courage because that would require defining units, but since "zero" doesn't require units, it is possible to have zero courage.
ell.stackexchange.com/users/419/supercat
“There was  zero courage  in this verdict,” he said. ”I think this goes to the jury not wanting to make a difficult decision."   I learned that mass nouns cannot be enumerated.   Yes, I know that  zero courage  can be replaced with  no courage , but, since  zero  is a number, I wonder whether  zero courage  is ungrammatical or only sloppy style.
Can "zero" be used to describe uncountable nouns?
ell.stackexchange.com
<nouns><uncountable-nouns>
ell.stackexchange.com/questions/4864
ell.stackexchange.com/users/None/
As an adjective , zero means the lowest possible amount or level, or nothing at all.  Based on this definition, it is correct to use it to describe a mass noun to say there is none of it.  Using "zero" instead of "no" is usually used to emphasize the lack of whatever it's describing. Zero is the lowest possible amount and can emphasise a lack. Using it bends the rules of ordinary usage and is synonymous with 'no'.
Zero is the lowest possible amount and can emphasise a lack. Using it bends the rules of normal usage and is synonymous with 'no'.