Grammar
Style guide 
fewer and less
Fewer and less are so commonly confused, it’s tempting to think that fewer may vanish from the language.
In the meantime, the distinction does still exist. Less means ‘not as much’ and fewer means ‘not as many’.
I drank less water than you.
She
drank fewer glasses of water than him.
In other words, we use fewer for objects we can count, such as days or people, and less for things that we can't count, such as energy or salt.
Just to demonstrate English's inconsistency though, we often use less when referring to numbers.
We spent less than $50 or 12 items or less (supermarket express lane).
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