Thereupon means immediately after something happens, or as a direct result of it. When you read that a character did something and thereupon something else occurred, it means the second thing happened right away because of the first.

You'll find this word mostly in stories and formal writing. A fairy tale might say: “The prince kissed the sleeping princess, and she thereupon awakened.” Or a historical account might read: “The general received news of the enemy's retreat and thereupon ordered his troops to advance.”

In everyday conversation, people usually say “then” or “right after that” instead. But thereupon adds a sense of importance and connection between events. It emphasizes that what happened next wasn't random but followed naturally or necessarily from what came before. When a judge announces a verdict and the defendant thereupon breaks down in tears, the word connects those two moments in a way that shows they’re linked.