To weaken means to make something less strong, powerful, or effective. When a fever weakens your body, you feel tired and shaky instead of energetic. When heavy rains weaken a dam, the structure becomes less able to hold back water. A weak argument in a debate becomes even weaker when someone points out its flaws.

The word applies to physical strength, like how illness weakens muscles, but also to less visible things. A crack weakens a wooden beam even if the beam still looks solid. Doubt can weaken someone's confidence before a big performance. When a team's star player gets injured, it weakens the whole team's chances of winning.

Notice that weakening often happens gradually. A bridge doesn't collapse immediately when rust begins to weaken its supports. A friendship doesn't end suddenly, but repeated arguments and broken promises can slowly weaken the trust between friends. Sometimes things weaken from direct attack, like how sunlight weakens certain types of fabric until they tear easily. Other times they weaken from neglect, like how unused muscles weaken over time.

The opposite of weaken is strengthen. While practice and exercise strengthen skills and muscles, laziness and lack of effort weaken them. Understanding what weakens or strengthens something helps you protect what matters most.