A biosensor is an analytical tool that detects a biological response and converts it into a measurable signal. It has five main components: an analyte, bioreceptor, transducer, electrical interface, and electronic system. The bioreceptor interacts specifically with the analyte, causing a change in the transducer that is converted into an electrical signal via the interface and processed by the electronic system. Common types include electrochemical, optical, thermal, and resonant biosensors. Examples of applications include food analysis, medical diagnosis, environmental monitoring, and more.