Radiation efficiency refers to the effectiveness of an antenna in converting input power into radiated electromagnetic energy. It is expressed as a percentage, indicating how much of the total power supplied to the antenna is actually emitted as radio waves. A higher radiation efficiency means that more energy is being radiated, while a lower efficiency indicates that some power is lost, often as heat. Factors affecting radiation efficiency include the antenna's design, materials, and operating frequency. For example, dipole antennas typically have high radiation efficiency, while poorly designed antennas may have significant losses. Understanding radiation efficiency is crucial for optimizing communication systems and ensuring effective signal transmission.