S.I unit of temperature:
Temperature is a measure of the average kinetic energy of the particles in a substance. The SI unit of temperature is Kelvin (K).
Temperature can also be measured in degrees Celsius (°C) and degrees Fahrenheit (°F), but Kelvin is the standard unit used in scientific calculations.

Details:

1. Kelvin (K):
- Kelvin is the base unit of temperature in the International System of Units (SI).
- It is defined based on the properties of water at its triple point, which is the temperature at which water can exist in all three states - solid, liquid, and gas.
- The Kelvin scale starts at absolute zero, which is the lowest possible temperature where particles have minimal kinetic energy.
- To convert Celsius to Kelvin, you can use the formula K = °C + 273.15.

2. Degrees Celsius (°C):
- Degrees Celsius is a commonly used unit of temperature in everyday life.
- It is based on the freezing and boiling points of water, where 0°C is the freezing point and 100°C is the boiling point at standard atmospheric pressure.
- To convert Kelvin to Celsius, you can use the formula °C = K - 273.15.

3. Degrees Fahrenheit (°F):
- Degrees Fahrenheit is another unit of temperature commonly used in the United States.
- It is based on a scale where 32°F is the freezing point of water and 212°F is the boiling point at standard atmospheric pressure.
- To convert Celsius to Fahrenheit, you can use the formula °F = (°C × 9/5) + 32.
In conclusion, the SI unit of temperature is Kelvin, which is widely used in scientific calculations and measurements. It is important to understand the different temperature scales and how to convert between them for various applications.

Kelvin which is equal to ⁰Celsius + 273.15!