An "emitter" is a device or component that produces or releases energy, particles, or signals. Common examples include light-emitting diodes (LEDs) that emit light when an electric current passes through them, and radio frequency emitters that transmit signals for communication. Emitters are essential in various technologies, including telecommunications, lighting, and sensors. They can be found in everyday items like remote controls, where infrared emitters send signals to devices, and in scientific applications, such as particle emitters used in research to study atomic and subatomic particles.