Testing means checking or examining something to find out how well it works, what it can do, or whether it's ready. When scientists test a new medicine, they carefully study whether it's safe and effective. When you test a rope bridge before crossing, you're making sure it can hold your weight. When your teacher gives you a math test, she's checking what you've learned.

Testing can also mean pushing something to its limits to see how much it can handle. An engineer might test a new airplane wing by bending it until it breaks, discovering exactly how strong it is. Athletes test themselves by training harder each day, finding out what their bodies can achieve. A friendship gets tested when times are difficult and you discover whether you can count on each other.

The word appears in many common expressions. When you're testing the waters, you're trying something carefully to see how it goes before fully committing. Scientists working in laboratories spend their days testing hypotheses, which means running experiments to see if their ideas about how nature works are correct. Companies hire beta testers to try out new video games or apps before releasing them to everyone, helping find problems that need fixing.