Fewer boys, less noise...

[ZeroSomeGameThingy]

Not a sociological observation. Did anyone learn a rule for this?

Fewer when you can separate the components and less when you can't. So there are several individual boys but one amount of noise and hence fewer boys and less noise.

Fewer for countables, less for partitives. More and some for both countables and partitives.

Or: if it makes sense with a numeral before it, fewer. Otherwise less.

But sometimes you would use a certain noun with a number but eschew it with a comparative of quantity. This happens with measures: Six pounds, less money; eighteen years old, younger; eight miles, less far.

"Components", "partitives" - both useful if I need to explain this to someone else. Thanks.

I am certain that no-one has been taught this since 1950.....

eight miles, less far.

Or nearer, closer or shorter. 'Less far' sounds odd.

'Fewer' for something you usually measure in integers.
'Less' for something you usually measure in decimals.

So fewer than 5 grains of sugar, but less than 1.5kg of sugar.

Because you can't have 0.3 of a boy, it's fewer boys.

Because you can have 40.25 decibels of noise, it's less noise.