……….. Errors are those errors which occure irregularly and by ……….

Explanation

To answer the question, we need to fill in the blanks with the appropriate terms related to errors in measurements. The question states: "……….. Errors are those errors which occur irregularly and by ………. "

### Step-by-Step Solution:

1. **Understanding the Types of Errors**:
- In physics and experimental science, errors can be categorized into systematic errors and random errors. Systematic errors are consistent and predictable, while random errors are irregular and unpredictable.

2. **Identifying the Correct Type of Error**:
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