Inverse means opposite or reversed. In mathematics, the inverse of a number or operation undoes what that number or operation does. The inverse of addition is subtraction: if you add 5 and then subtract 5, you're back where you started. The inverse of multiplication is division: multiplying by 4 and then dividing by 4 brings you back to your original number.

The word appears in many contexts beyond math. If you walk forward and then walk in the inverse direction, you're retracing your steps backward. In an inverse relationship, when one thing goes up, the other goes down: the faster you pedal your bike, the less time it takes to reach your destination. Speed and travel time have an inverse relationship.

Scientists use inversely when describing how variables relate: as temperature increases, hot chocolate sales decrease. These patterns move in opposite directions.

The word can also describe physical opposites. If you look at writing in a mirror, you see its inverse: backward and reversed. When you flip a fraction upside down (turning 3/4 into 4/3), you've found its multiplicative inverse.

Think of inverse as the mathematical and logical version of “opposite”: whatever something does, its inverse undoes it or reverses it.