Usage The adjectives less and fewer have similar meanings but are used in slightly different ways. Fewer is used with nouns that can be counted.

• classrooms with fewer students

• They have fewer than three children.

Less is usually used with nouns that cannot be counted.

• He makes less money than she does.

• The new model uses less power.

But less is also more likely than fewer to be used with count nouns that refer to distances and amounts of money.

• an investment of less than $2,000

• It's less than 100 miles away.

Less is also used in mathematical expressions and in certain phrases.

• an angle of less than 180 degrees

• Write it in 25 words or less.

It is also used instead of fewer with other sorts of plural nouns, although many people still consider this use incorrect.

• Less than 10 people showed up. = Fewer than 10 people showed up.

《韦氏高阶》less 词条下的用法提示。