Reactions involving migration of an atom or a group from one atom to another within the same molecule are called .. .... .. .. reactions.

Explanation

To solve the question regarding the type of reactions that involve the migration of an atom or a group from one atom to another within the same molecule, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Concept**: We need to identify the type of reaction where an atom or a group migrates from one part of a molecule to another part of the same molecule. This is a fundamental concept in organic chemistry.

2. **Identifying the Term**: The term that describes this type of reaction is crucial. In organic chemistry, reactions that involve the rearrangement of atoms or groups within a molecule are commonly referred to as "rearrangement reactions."

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