A breakthrough is a sudden, important discovery or achievement that solves a difficult problem or opens up new possibilities. When scientists achieve a breakthrough in cancer research, they find something that could help save lives. When an inventor makes a breakthrough, they figure out how to make something work that nobody could create before.

Breakthroughs often come after long periods of hard work and frustration. Thomas Edison tried thousands of materials before his breakthrough with the light bulb filament. Marie Curie worked for years before her breakthrough discoveries about radioactivity. A student struggling with long division might suddenly have a breakthrough when the concept finally clicks into place.

The word suggests breaking through a barrier or wall that was blocking progress. Imagine pushing against a locked door for hours, then finally finding the key. That moment when the door swings open is like a breakthrough: you've gotten past an obstacle that seemed impossible to overcome.

Breakthroughs can be big or small. A medical breakthrough might change millions of lives, while a personal breakthrough might mean finally mastering a skateboard trick you've been practicing for months. Either way, a breakthrough represents that exciting moment when persistence and effort finally pay off, and something that seemed impossible becomes possible.