Chain isomerism is also referred to as ......... isomerism.

Explanation

**Step-by-Step Text Solution:**

1. **Understanding Chain Isomerism:**
- Chain isomerism occurs when two or more compounds have the same molecular formula but differ in the arrangement of carbon atoms. This can be in the form of straight chains or branched chains.

2. **Definition of Chain Isomers:**
- The compounds that exhibit chain isomerism are referred to as chain isomers. They have identical molecular formulas but different structural arrangements.

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