Define SI unit. Write the unit of the following fundamental quantity in SI system.
(i) Temperature
(ii) Length

Explanation

### Step-by-Step Solution:

1. **Define SI Unit**:
The SI unit, or the International System of Units, is a standardized system of measurement that is used globally for scientific and technical purposes. It provides a consistent framework for measuring various physical quantities, ensuring that measurements are universally understood and comparable.

2. **Importance of SI Units**:
The importance of SI units lies in their ability to provide a common language for scientists and researchers around the world. This uniformity helps avoid confusion and errors that may arise from using different measurement systems.

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