The instrument used to measure temperature is called a thermometer. Thermometers can be found in various forms, including digital, mercury, and alcohol-based models. They work by measuring the expansion or contraction of a liquid (in traditional thermometers) or using electronic sensors in digital versions. Thermometers are essential in many fields, such as meteorology, healthcare, and cooking. Accurate temperature measurement is vital for monitoring weather conditions, diagnosing illnesses, and ensuring food safety.