To propagate means to spread or multiply something, making more of it or helping it reach new places. When gardeners propagate plants, they grow new ones from seeds, cuttings, or roots. A farmer might propagate tomato plants by saving seeds from this year's best tomatoes to plant next spring. Some plants propagate themselves naturally: dandelions send their seeds floating through the air on tiny parachutes, spreading across lawns and fields.

The word also describes how ideas, information, or beliefs spread from person to person. When you hear an interesting fact and share it with your friends, who then tell their families, you're all helping to propagate that information. Rumors propagate quickly through a school. Scientists propagate their discoveries by publishing research papers. Social media can propagate news, both true and false, around the world in minutes.

You'll often see propagate in science contexts. Sound waves propagate through air. Light propagates through space. Radio signals propagate from transmission towers to your car's antenna.