"Radioactive" refers to the property of certain materials that emit radiation as they decay. This process occurs when unstable atomic nuclei lose energy by releasing particles or electromagnetic waves. Common radioactive elements include uranium, radium, and plutonium, which are often found in nature or produced in nuclear reactors. The term is also associated with the effects of radiation on living organisms. Exposure to high levels of radiation can lead to health issues, including cancer. Safety measures, such as shielding and distance, are essential when working with or around radioactive materials to minimize risks to human health and the environment.