Inconsistent means not staying the same or not matching up with itself. When something is inconsistent, it changes in ways that don't make sense or it contradicts itself.

A basketball player who scores 30 points one game and only 2 the next is playing inconsistently. Their performance keeps changing unpredictably. A friend who acts nice one day and mean the next is being inconsistent. You never know what to expect.

The word also describes things that don't line up logically. If someone says they love animals but refuses to help a lost puppy, their actions are inconsistent with their words. When a student claims they studied hard but can't answer basic questions, those two facts seem inconsistent.

Scientists look for consistency in their experiments. If an experiment produces different results each time under the same conditions, something inconsistent is happening that needs explaining.

In math, inconsistent equations have no solution that works for all of them at once. If one equation says x equals 5 and another says x equals 7, they're inconsistent because x can't be both numbers at the same time.

The opposite of inconsistent is consistent: reliable, matching, staying the same. Consistent people keep their promises. Consistent students turn in quality work regularly. Consistency builds trust because others know what to expect.