Substances which do not burn easily are called ______.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the term that describes substances that do not burn easily.

2. **Identifying the Term**: The term used to describe substances that do not ignite or support combustion is "non-combustible."

3. **Definition of Non-combustible**: Non-combustible substances are those that do not support ignition or combustion. This means they do not catch fire or burn under normal conditions.

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