Fruit is uncountable but vegetables is countable, so we should use less or fewer before them together?
Learn English – Should we say less or fewer “fruit and vegetables”
compoundscountable-nounsgrammaruncountable-nouns
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*Disclaimer: this answer is based on a grammatical standard, which has been shown to be a "myth" in a response to a related question "Less" vs. "fewer". I posted my answer here before reading the previous discussion on this whole issue of "less" versus "fewer". I would like to make it clear that my views are not based on some pretentious notions of superior knowledge of grammar. This is simply a standard I have always followed based on my background in English. I leave it to the reader to decide what they want to stick to. Thanks.
Indeed, one should use "fewer" for countable quantities. In fact, the usage of "less" for such quantities is grammatically incorrect. Also, I agree that a percentage is really a fraction. As such, it is apparently not a countable quantity in the grammatical sense. But, there's a catch! The word "percent" means "one part out of every hundred". Thus, if the percentage turns out to be countable, then one gets a countable quantity. When referring to a group of people, this is usually the case. Therefore, in your example sentence, the absolutely correct choice would be "fewer":
Fewer than 10.7% of the people were happy.
As the subject of the sentence "fewer than 10.7%" is certainly a countable quantity.
Now, for a counter example using cake! A fraction of a cake is not countable, no matter how you look at it. Thus, this example is correct:
Less than 10.7% of the cake was eaten.
(although 10.7% is a very arbitrary fraction to use for cake!)
In general, the rule* for percentages would be:
- Use "less" with percentages of uncountable nouns
- Use "fewer" with percentages of countable nouns
Fewer is used when referring to countable quantities (in which case the noun is usually in plural), and less is used when referring to uncountable quantities (in which case the noun is usually in singular). So I would say fewer cows, but less milk.
If I understand correctly, a ply is a layer. So plies would be countable quantity, just like layers, and I would say fewer plies as you suggested yourself.
However, I can imagine that there could be situations where the word ply is sometimes used informally for something made of layers, for example as a shortening of plywood. In which case you could say ''less ply'' in this context, as it would actually be short for ''less plywood'', which is fine.
Best Answer
I'll assume you're using fruit in its more common, uncountable sense.
We say "less fruit", because fruit is uncountable in this sentence, and "fewer vegetables" because vegetables is countable. When fruit and vegetables are combined, the rule of proximity tells us that the word nearest to less / fewer determines which form we should use.