than
A word used to compare one thing with another.
Than is a word used to compare two things. When you say one thing is bigger, faster, stronger, or better than another, you're using than to show the difference between them.
You might say your sister is taller than you, or that summer feels hotter than spring. When you finish a race faster than your previous time, you're comparing your current performance to your past one. If you'd rather play outside than do homework, you're expressing which choice you prefer.
Than always involves a comparison: you're measuring one thing against another. “I have more baseball cards than you do.” “This puzzle is harder than the last one.” “She studies more than anyone else in the class.”
Be careful not to confuse than with then. Than compares (bigger than), while then relates to time (we ate lunch, then went outside). An easy way to remember: if you're comparing two things, you need than.