Fill in the blanks.
An algebraic expression is called an equation if it involves an ______________.

Answer

To fill in the blank in the statement, we need to understand the definition of an equation in algebra.

1. **Understanding the terms**:
- An algebraic expression is a combination of numbers, variables, and operations (like addition, subtraction, multiplication, and division).
- An equation is a statement that two expressions are equal, which is indicated by an equality sign.

2. **Identifying the key feature of an equation**:
- The main characteristic that distinguishes an equation from a mere algebraic expression is the presence of an equality sign.

3. **Filling in the blank**:
- Therefore, we can fill in the blank with the term "equality sign".

Final answer: An algebraic expression is called an equation if it involves an **equality sign**.

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