Thermometers are essential tools used to measure temperature. There are various types of thermometers, each with its specific application. Some of the most common synonyms for thermometers include temperature gauge, thermostat, pyrometer, thermocouple, and thermistor. Temperature gauge and thermostat are mostly used for measuring the temperature of liquids and gases in industrial settings. Pyrometers are used for high-temperature applications, like measuring the temperature of furnaces and engines. Thermocouples are used in scientific and medical applications, and thermistors are commonly used in electronic devices. Regardless of the type of thermometer, all work using the basic principle of thermal expansion to determine temperature.