Fahrenheit (°F)
Definition: Fahrenheit (symbol: °F) is a temperature scale based on one proposed in 1724 by the physicist Daniel Gabriel Fahrenheit. It uses the degree Fahrenheit as the unit. Several accounts of how he originally defined his scale exist, but the original paper suggests the lower defining point, 0 °F, was established as the freezing temperature of a solution of brine made from a mixture of water, ice, and ammonium chloride (a salt).
History/origin: The Fahrenheit scale was the primary temperature standard for climatic, industrial, and medical purposes in most English-speaking countries until the 1960s, when it was largely replaced by the Celsius scale.
Current use: The Fahrenheit scale is still used in the United States and some other countries for everyday temperature measurements, such as weather forecasts and cooking.
Celsius (°C)
Definition: Celsius (symbol: °C) is a temperature scale based on 0° for the freezing point of water and 100° for the boiling point of water. It is the most widely used temperature scale in the world, except in the United States.
History/origin: The Celsius scale was invented in 1742 by the Swedish astronomer Anders Celsius. It was originally defined with 0° as the boiling point of water and 100° as the freezing point, but this was later reversed.
Current use: The Celsius scale is used worldwide for scientific and everyday temperature measurements. It is the standard unit of temperature in the International System of Units (SI).