A thermometer measures the temperature of things. "Thermo" means heat, and "meter" means to measure. A thermometer is capable of measuring the temperature of a wide range of objects and the temperatures of individuals. These measurements include body temperature, oven temperature and outside temperature.
A red or silver line in a bulb thermometer goes up if the temperature increases or down if it decreases.
Spring thermometers are less accurate than bulb thermometers and use coiled, temperature-sensitive pieces of metal. One end of a coil is connected to a pointer that moves higher or lower depending on the temperature.
In the United States, thermometer measurements are usually calculated in degrees Fahrenheit. Most other countries, along with the scientific community, use degrees Celsius, although some scientists use Kelvin.