For example:
I need a tire with less ply.
or
I need a tire with fewer ply.
Is "less" correct because ply is a singular noun? Or should it be "fewer" because it refers to a specific count of plied material? Or should "fewer plies" be used to reduce ambiguity?
A quick Google search seems to show that "fewer ply" is much more common. However, it could lead to confusion in the example below:
Continuing trend toward fewer ply tires is expected." –Technological trends in major American industries
It might seem that it refers to the number of tires as opposed to the having fewer plies, which seems to be the intention.
Another example could be toilet paper:
I normally use 3 ply, but now I am searching for a brand with (less/fewer) ply.
Best Answer
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.