1. the emission of radiation from the nuclei of unstable atoms
Usage: physics

Examples

• Scientists measured the radioactivity levels near the nuclear plant.
• The radioactivity of uranium makes it useful for generating electricity.
• Geiger counters detect radioactivity in the environment.
• The radioactivity from the medical isotope helped doctors see inside the patient’s body.
• After the accident, radioactivity contaminated the surrounding area.
• Natural radioactivity exists in many rocks and minerals.