Certainly, ‘dew’ is normally uncountable, but the writer precedes it here with the indefinite article for literary effect. Other meteorological phenomena, such as fog and mist, can be treated in the same way. It's not at all a stupid question.
The Wikipedia entry for mass nouns notes:
In linguistics, a mass noun, uncountable noun, or non-count noun is a
noun with the syntactic property that any quantity of it is treated as
an undifferentiated unit, rather than as something with discrete
subsets. Non-count nouns are distinguished from count nouns.
Given that different languages have different grammatical features,
the actual test for which nouns are mass nouns may vary between
languages. In English, mass nouns are characterized by the fact that
they cannot be directly modified by a numeral without specifying a
unit of measurement, and that they cannot combine with an indefinite
article (a or an). Thus, the mass noun "water" is quantified as "20
litres of water" while the count noun "chair" is quantified as "20
chairs". However, both mass and count nouns can be quantified in
relative terms without unit specification (e.g., "so much water," "so
many chairs").
Some mass nouns can be used in English in the plural to mean "more
than one instance (or example) of a certain sort of entity"—for
example, "Many cleaning agents today are technically not soaps, but
detergents." In such cases they no longer play the role of mass nouns,
but (syntactically) they are treated as count nouns.
It also observes:
Some nouns have both a mass sense and a count sense (for example,
paper).
Cheese appears to be another of these nouns with both a mass sense and a count sense. The Oxford Dictionaries website includes the following as a definition of cheese:
[COUNT NOUN] A complete cake of cheese with its rind.
It offers the following example sentence:
"the cheeses are trimmed and wrapped in sterilized muslin."
This is sufficient to reassure me that I could legitimately say, "Nine of the cheeses are finished and we have three more to go." The word cheese can, then function as both a mass noun and a count noun, meaning slightly different things in the two uses.
It also seems clear that most mass nouns can make an appearance as a count noun. The Wikipedia article cited above notes:
Some mass nouns can be used in English in the plural to mean "more
than one instance (or example) of a certain sort of entity"—for
example, "Many cleaning agents today are technically not soaps, but
detergents." In such cases they no longer play the role of mass nouns,
but (syntactically) they are treated as count nouns.
I've tried but haven't been able to find an example of a noun that cannot become a count noun in this way.
The lab tested 7 gasolines. 12 different coffees are on offer.
I admit that I would like the sentence above better if it said "7 brands of gasoline" or "7 samples of gasoline", but nothing about it seems to me wrong or even particularly surprising. Even abstract nouns seem to be amenable to this transformation:
FDR's Four Freedoms
10 Hopes I Have For Past Loves (Title of Huffington Post Article)
Best Answer
As Gregory Bateson put it in "Every Schoolboy Knows",
It is tricky, and it's not ideal, but there you are. That's language.
In English, nouns that normally refer to objects that can be identified as units have different rules (singular indefinite article, pluralization) than other nouns that refer mostly to
These are "mass nouns", and can be pluralized, or otherwise used like count nouns. As noted,
this means different kinds (types, varieties, brands, categories) of the otherwise mass noun.
In addition to this conventional countification of mass nouns, indicating varieties,
there is also a conventional massification of count nouns, indicating essence.
X.This is English. But in many languages that use numeric classifiers (Malay, Burmese, Mandarin, Japanese), there's no distinction to speak of between mass and count -- all nouns are mass nouns, and if you need to count or otherwise distinguish what English would use a count noun for, you simply use a classifer instead. For instance, Japanese
English doesn't have numeric classifiers, so we can't use this strategy.