A millivolt (mV) is a unit of electric potential equal to one-thousandth of a volt. It is commonly used in various electrical and electronic applications to measure small voltages. For example, in medical devices like electrocardiograms (ECGs), millivolts help monitor heart activity by detecting tiny electrical signals generated by the heart. Millivolts are essential in fields such as telecommunications and sensor technology, where precise voltage measurements are crucial. Understanding millivolts allows engineers and technicians to design and troubleshoot circuits effectively, ensuring optimal performance in devices ranging from smartphones to industrial equipment.