To theorize means to form ideas or explanations about how something works when you don't yet have all the facts. When scientists theorize about why dinosaurs went extinct, they're developing possible explanations based on the evidence they've found: fossils, rock layers, and crater marks that might point to an asteroid impact.

Theorizing is different from guessing randomly. When you theorize, you use what you already know to build a logical explanation for something you're trying to understand. A detective theorizes about how a theft happened by examining clues at the scene. Students might theorize about what's inside a wrapped present by noticing its weight and shape.

Good theorizing leads to testing. After scientists theorize that an asteroid killed the dinosaurs, they search for more evidence to support or challenge that theory. Your theorizing about what's for dinner based on the smell from the kitchen gets confirmed when you sit down at the table.

People theorize about everything from how magic tricks work to why their friend seemed upset at lunch.