Fewer and less both represent the opposite of the comparative adjective more. However, the main difference between fewer and less is to deduce whether fewer and less will be working with a countable or uncountable noun in the given sentence.
People often confuse when to use less and when to use fewer in a sentence. Here are some tips on how to use fewer and less correctly though there are some exceptions to the general rules about their usage.
Use fewer if you are referring to people or things in the plural (e.g. apples, books, cookies, boys, students). For example:
People these days are buying fewer gold bars. (gold bars countable)
Fewer entrepreneurs have invested in real estate lately. (entrepreneurs countable)
Use less when you are referring to something that can’t be counted or doesn’t have a plural (e.g. sugar, money, milk, time, music, rain). For example:
People these days are buying less gold jewellery. (jewellery uncountable)
In these precarious times, people are looking to spend less money. (money uncountable)
Some example sentences of fewer
If fewer people used polythene waste on hills, there would be less of a threat to the ecosystem.
Fewer people smoke these days than used to.
We received far fewer lawsuits of divorce this year than expected.
Fewer than 3,500 tigers are left in the wild today.
Sam made fewer grammatical mistakes than sally (did) in essay competition.
Your guitar left me with less space in the car.
Some example sentences of less
Lisa now wants to spend less time with her in-laws. (determiner – a smaller amount of; not as much)
Ironically, when she was in hospital, she listened to less music.
Less is also used with numbers when they are on their own and with expressions of measurement or time, e.g.:
The baby is born weighing less than 5 pounds.
Their relationship lasted less than six months.
Brooklyn is less than 8 miles away from Madison Square Garden Center.
The child mortality is now less of a problem than it used to be. (pronoun – a smaller amount or quantity of something)
They covered that much distance in less than an hour.
Pitcairn Island has less than 50 inhabitants; most reside near the village of Adamstown.
‘Avoid less important question in studies’ (adverb – to a smaller extent; not so much)
Emma has less than fifty dollars left on her trip to Wagner Vineyards. (though we can count money, it is common sense to think of money as a bulk quantity rather than an aggregate of currency units. So, we use less rather than fewer.
Emma has fewer than fifty dollars left on her trip to Wagner Vineyards. (not wrong but would seem awkward and unexpected to the listener)
Now that it is clear to you as to where to use fewer and where to use less, you are less likely to make mistakes in the usage of these words. However, you have to be more careful in formal writing. In informal writing or speech, it all depends on which one sounds better to your ear.