A stethoscope is the device that doctors and nurses use to listen to your heartbeat. Many medical workers walk around wearing stethoscopes around their necks.
Made up of the Greek stethos, "chest or breast," and the suffix -scope, "an instrument for seeing," the meaning of stethoscope is fairly straightforward. It's an instrument that's used to "see," or more accurately, to hear, inside your chest. During a medical exam, your doctor will listen to your heartbeat and the sound your lungs make as you breathe deeply. Veterinarians use stethoscopes too, for listening to their animal patients' hearts and lungs.