Fewer and Less

We use fewer for items that we can count; we use less for items we cannot count:

I have fewer students in this class than I had in last year’s class.

My brother prefers less milk in his coffee than his wife does.

How can you differentiate between count and non-count items?  One way is to imagine that you have an armful of the item and that you place the armload on the table.  If you can easily identify each of the items, they are count: oranges, cups, pencils, logs, papers, etc.  If the items are too small or if they would flow off of the table, they are non-count: orange juice sugar, water, sawdust, pulp, etc.

Resources

Merriam-Webster discusses the exceptions to this common rule.

 

Oxford Dictionaries and The New York Times explain this difference simply and they provide good examples.

ProProfs has a good interactive quiz.