Hysteria is an old-fashioned word for extreme, uncontrollable emotion or panic, especially when it spreads quickly through a group. When a crowd breaks into hysteria at a concert, people might scream, cry, or lose control of themselves. When news of something frightening causes mass hysteria in a town, people might panic and make irrational decisions based on fear rather than facts.

Imagine a classroom where one student screams about seeing a spider, then others start screaming too, jumping on desks and running around, even though most of them never saw the spider at all. That escalating panic is hysteria, where emotion overwhelms reason and spreads like wildfire.

The word has a complicated history. Doctors once used it as a medical diagnosis, wrongly claiming it was a disease that only affected women. That idea was based on prejudice, not science. Today, calling someone hysterical can sound dismissive, as if you're saying their feelings don't matter. The word works better for describing situations, like hysterical laughter (uncontrollable giggling) or the hysteria of a crowd, than for labeling a person.