When two things are incompatible, they can't work together or exist together successfully. Like trying to play a PlayStation game in an Xbox console, or mixing oil and water, incompatible things just don't fit.

You might discover that two software programs are incompatible with each other, causing your computer to crash when you try to run them at the same time. A new printer might be incompatible with an older computer's operating system. In science class, you might learn that certain chemicals are incompatible and should never be mixed because they create dangerous reactions.

The word also describes people whose personalities, goals, or values clash so much that they can't get along. Two friends might have incompatible ideas about how to spend their weekend: one wants quiet time reading while the other wants to play loud video games. This doesn't make either person wrong, just incompatible in that moment.

The opposite is compatible, meaning things that work well together. When something is incompatible, there's a fundamental mismatch that prevents harmony or function. Understanding incompatibility helps you avoid frustration because you learn to check whether things can work together before assuming they will.