A thermometer is a device used to measure the temperature of a body or object. Some of the most important types of thermometers are liquid-in-glass, bimetallic, digital, infrared, and gas thermometers. Thermometers measure temperature on three main scales: Celsius, Fahrenheit, and Kelvin. These scales were designed based on the freezing and boiling points of water. On the Celsius temperature scale, the freezing point of water is labeled as zero, whereas the boiling point of water is labeled as one hundred. There are one hundred degree intervals between these two points, which is why it is also known as the centigrade scale. Here, the unit of temperature is degree Celsius. On the Fahrenheit temperature scale, the freezing point of water is indicated at 32, while the boiling point is 212. The unit of temperature on this scale is degree Fahrenheit. Temperature on the Fahrenheit scale can easily be converted to Celsius by employing the conversion equation. The Kelvin temperature scale is an absolute temperature scale. Here, zero kelvin indicates absolute zero, which is the lowest possible temperature.