Less and Many : When should I use LESS and when should I use FEWER?
Less means not as much. Fewer means not as many.
• A shower takes less water than a bath, so take fewer baths and more showers.
This can be tricky when referring to quantities. For example, we say less than six weeks, NOT fewer than six weeks because we are not referring to six individual weeks, but to a single period of time lasting six weeks.
However, it is always strictly incorrect to refer to less people. People are individuals and come in numbers, not in amounts.