A thermometer is the instrument typically used to measure temperature. Thermometers come in various designs and can utilize different substances, such as mercury or alcohol, that expand and contract with temperature changes. The most common types are liquid-in-glass thermometers, digital thermometers, and infrared thermometers. Liquid-in-glass thermometers are often used in laboratories and weather stations, while digital thermometers provide instant readings and are commonly used in homes. Infrared thermometers, which measure the infrared radiation emitted by an object, are especially useful for measuring the temperature of surfaces without direct contact.