To exclaim means to cry out suddenly with strong feeling. When you exclaim something, you burst out with surprise, excitement, anger, or joy. If you open a present and shout “I can't believe it!”, you're exclaiming. When your friend sees a spectacular sunset and yells “Look at those colors!”, that's an exclamation.

The word captures that moment when feelings are so strong that they jump out of your mouth before you can stop them. You might exclaim in delight when you find out school is canceled for a snow day, or exclaim in frustration when you realize you left your homework at home. Scientists exclaim when experiments work after months of failures. Athletes exclaim when they win championships.

Writers show exclamations with exclamation points, which makes sense: those punctuation marks try to capture on paper what your voice does naturally when strong emotions take over. The key is that exclaiming happens suddenly and intensely. You don't exclaim in a quiet, measured voice. You burst out, and everyone nearby knows exactly how you feel.