A cascade is a small waterfall, or a series of waterfalls flowing down from one level to another. Picture water tumbling down rocky steps in a forest stream, each little drop creating the next one below it.

The word also describes anything that happens in stages, with each event triggering the next one. When a teacher knocks over a pencil that bumps a book that pushes a water bottle off the desk, that's a cascade of accidents. In your body, a cascade of chemical reactions happens every time you eat: your stomach produces acid, which signals other organs to release digestive enzymes, which break down food into nutrients.

Sometimes cascade means a sudden rush or flow of many things at once. A cascade of questions might follow an interesting announcement in class. Bad news can trigger a cascade of problems, like when forgetting your homework leads to a poor grade, which leads to missed recess, which makes you grumpy with your friends.

As a verb, to cascade means to fall, pour, or happen in a cascading way. The image of water flowing downward captures something important: cascades have momentum. Once they start, each stage flows naturally into the next, gathering force as they go.