The Kelvin is the base SI unit for thermodynamic temperature. It is defined based on the triple point of water, where the temperature is 273.16 K. The Kelvin scale has the same increments as the Celsius scale, with 0 K equivalent to -273.15 degrees Celsius.
The Celsius scale is widely used in everyday life and scientific applications. It is defined based on the freezing and boiling points of water at standard atmospheric pressure. The Celsius scale has 100 equal divisions between the freezing and boiling points, with 0 °C representing the freezing point and 100 °C representing the boiling point of water at sea level.
The Fahrenheit scale is commonly used in the United States and some other countries for everyday temperature measurements. It is defined based on the freezing and boiling points of water. The Fahrenheit scale has 180 equal divisions between the freezing and boiling points, with 32 °F representing the freezing point and 212 °F representing the boiling point of water at sea level.
The Rankine scale is an absolute temperature scale similar to the Kelvin scale, but it uses Fahrenheit degrees instead of Celsius degrees. One Rankine degree is equal to one Fahrenheit degree, so the zero point on the Rankine scale is absolute zero (-459.67 °F).
