"Less" vs "fewer" - when to use each one

• "Fewer people came than expected."
• "Fewer than five mistakes."
• "I have fewer books than she does."

• "Less water."
• "Less time."
• "Less traffic."
• "Less money." (money is measured, not counted individually)

Can you count individual units? Fewer people (1 person, 2 people). Can't count individual units? Less water (not "one water, two waters").

"10 items or less" is technically incorrect - it should be "10 items or fewer." Most native speakers don't notice or care.

Time and distance often use "less" even though they're technically countable: "less than five minutes," "less than three miles." This is standard and accepted.

The fewer/less distinction matters in formal writing. In casual speech, "less" is commonly used for both.