Unlike means different from or not similar to something else. When you say one thing is unlike another, you're pointing out how they don't match or share the same qualities.

You might notice that today's weather is unlike yesterday's: yesterday was sunny and warm, while today is cold and rainy. A teacher might observe that your approach to solving a math problem is unlike your classmate's method, even though you both got the right answer. When you read that a character in a story acts unlike her usual self, you know she's behaving differently than normal.

The word helps us make comparisons by highlighting contrasts. If someone says “unlike most cats, my cat loves swimming,” they're emphasizing how unusual this particular cat is. If your friend says “unlike you, I actually enjoy eating Brussels sprouts,” they're pointing out a difference in your tastes.

Unlike can also mean not typical or characteristic of someone: “It's unlike him to forget his homework” suggests that forgetting homework doesn't match his normal, responsible behavior.