To solidify means to become solid or to make something solid. When you pour hot candle wax into a mold and let it cool, the liquid wax solidifies into a hard shape. Water solidifies into ice when it freezes. Concrete solidifies as it hardens, transforming from a thick liquid mixture into the foundation of a building.

The word also describes making something stronger, more certain, or more established. When a basketball team wins several games in a row, they solidify their position at the top of the standings. A scientist might perform additional experiments to solidify her conclusions, making them more convincing and reliable. When you practice multiplication tables until you know them perfectly, you're solidifying your understanding.

In both uses, the idea is the same: something becomes firmer, more permanent, and less likely to change. A friendship solidifies when you and another person spend time together and develop real trust. A plan solidifies when you work out all the details and everyone agrees on what to do. The transformation from liquid to solid gives us a perfect picture of what solidify means: taking something fluid or uncertain and making it stable and dependable.