............... are groups of letters that formed the same words when read from both forward and backward.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a term that describes groups of letters that form the same words when read from both forward and backward.

2. **Identifying the Concept**: The concept being described is related to words that maintain their spelling regardless of the direction from which they are read.

3. **Example of the Concept**: An example of such a word is "madam." When read from left to right, it spells "madam," and when read from right to left, it also spells "madam."

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