The device used to measure temperature is called a thermometer. Thermometers come in various types, but the most common ones include mercury, digital, and infrared thermometers. A traditional mercury thermometer contains mercury that expands and contracts in response to temperature changes, allowing for accurate readings. Digital thermometers use electronic sensors to provide rapid, precise measurements and are often used in medical settings. Infrared thermometers can measure temperature from a distance by detecting heat radiation emitted by objects, making them useful in both medical and industrial applications. Each type of thermometer serves specific purposes, ensuring accurate temperature assessment.