Teocht Tiontaire {category}

Celsius is the SI-accepted temperature scale defined by two fixed points: the freezing point and boiling point of water at standard atmospheric pressure. It's the default temperature scale for most of the world.

Fahrenheit is the temperature scale used in the United States and a few Caribbean nations. Unlike Celsius or Kelvin, it doesn't directly align with water's properties for easy conversion, making it less practical for scientific work but still prevalent in everyday American use.

Kelvin is the SI base unit of thermodynamic temperature. Unlike Celsius or Fahrenheit, Kelvin is an absolute scale with its zero point at absolute zero (the lowest possible temperature), making it ideal for scientific calculations.

Rankine is a less common absolute temperature scale that combines the Fahrenheit scale size with the absolute zero reference point of Kelvin. It's sometimes used in engineering contexts, particularly in the United States.