An algebraic expression is a numerical expression that contains a variable.
For example, below we have a numeric expression, and an algebraic expression. The second expression is algebraic because it contains a variable, x.
2 + 4
2x + 4
Let's try an example. Which of the below expressions is not an algebraic expression?
4x + 2x + 10
10k + 22h - 4
18 + 22
The final equation, 18 + 22, is not an algebraic expression because it does not contain a variable.