Discuss why lubricants are used in machine parts

Explanation

### Step-by-Step Solution:

1. **Definition of Lubricants**:
- Lubricants are substances that are applied to surfaces in mutual contact to reduce the friction between them.

2. **Function of Lubricants**:
- The primary function of lubricants is to decrease friction. They achieve this by filling the microscopic irregularities present on the surfaces of machine parts.

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