To differ means to be unlike or distinct from something else. When two things differ, they're not the same in some important way. Your opinion might differ from your friend's about which book is best, or siblings might differ in personality even though they grew up in the same house.

The word often appears when comparing things. Scientists study how animals differ from one another: a dolphin and a shark might look similar, but they differ in crucial ways (one is a mammal, the other is a fish). Climate patterns differ across regions. Teaching methods differ from school to school.

You can also use differ when you disagree with someone, though it sounds more formal and polite than simply saying “I disagree.” When you say “I differ with you on that point,” you're acknowledging the disagreement without making it sound like a fight. There's even a phrase, “agree to differ,” which means accepting that you and another person see things differently and that's okay.

The related word difference is the noun form: the difference between two things is how they're not alike. Someone who makes a difference creates meaningful change. Different is the adjective: things that are different are not the same.