We say less cheese (a non-countable noun) and fewer sausages (a countable noun). The difference between less and fewer is whether the noun is "countable".
What I don't understand is why we say "less than 9 sausages" (a countable noun compared to a number). As far as I can tell, you use "less" if the noun is unspecific (non-countable), "fewer" if it's fairly specific (countable) but "less" if it's very specific (countable and compared to a number).
Can anyone tell me why increasing the specificity of the phrase changes the word from "less", to "fewer", then back to "less" again?
