Less means a smaller amount of something. When you have less homework tonight than last night, you don't have as much to do. When your glass has less water than your friend's, yours isn't as full.

The word works best with things you can't easily count as separate items. You have less sand, less time, less noise, or less patience. For things you can count individually, like cookies or books, you usually use fewer instead: “fewer cookies,” not “less cookies.” Think of it this way: if you can count them one by one, use fewer. If it's more of a general amount or mass, use less.

Less can also mean “minus” in math: ten less three equals seven. And when someone is less than impressed with your excuse for being late, they're not impressed at all. The phrase suggests they're actually disappointed or skeptical.